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THIS book has been prepared in the hope that a concise state- 
ment of the facts and more important hypotheses concerning resist- 
ance to infection may serve to provide a clear understanding of a 
subject of the utmost importance in modern diagnosis and treat- 
ment. Designed primarily for students of medicine and for those 
practitioners whose duties have made it impossible to digest a large 
mass of publications on the subject, the scope of the book is 
restricted to fundamental principles. The plan throughout is to pre- 
sent on an experimental basis the demonstrated facts and to supple- 
ment these with brief discussions of the practical and theoretical 
bearing of the phenomena upon resistance and disease in man. A 
few illustrations have been inserted, but it must be recognized that 
technical details can only be fully comprehended on the basis of 
actual work with the methods. The usual diagrams of the side- 
chain theory have been omitted because of the belief that they 
serve to confuse rather than clarify the conception of processes 
whose fundamental basis lies in the field of physical chemistry. 
Certain material concerning the practical application of immunology 
to the prevention and cure of disease has been collected in three 
appendices. These have been added in order to explain the basis of the 
practical methods rather than as an exact guide in their application. 

Knowledge progresses from the known to the unknown, from 
the simple to the complex, and if the brevity of the book serves to 
implant essentials in such a way that the reader not only grasps the 
facts, but finds himself stimulated to seek further information and 
discussion in more comprehensive works, the most compelling aim 
of this book will have been achieved. For this purpose books 
which we have used with considerable freedom are recommended: 
Zinsser, " Infection and Resistance " ; Wells, " Chemical Pathol- 
ogy " ; Kolmer, " Infection, Immunity, and Specific Therapy " ; 
Kraus and Levaditi, " Handbuch der Technik und Methodik der 
Immunitatsforschung " ; Muir, " Studies on Immunity " ; Kolle and 
Wassermann, " Handbuch der pathogenen Mikroorganismen " ; 
Metchnikoff, " Immunity in Infective Diseases " ; Bordet, " Traite de 
I'lmmunite dans les Maladies Infectieuses "; Besredka, " Anaphy- 
laxis and Antianaphylaxis " ; Bordet and Gay, " Studies in 
Immunity " ; Gay, " Typhoid Fever " ; Browning, " Applied Bacteri- 
ology " ; Craig, " The Wassermann Test " ; Noguchi, " Serum 
Diagnosis of Syphilis " ; Zinsser, Hopkins, and Ottenberg, " Lab- 
oratory Course in Serum Study." The names of those who have 
contributed to the literature are given in the text, but precise refer- 
ences have been omitted, since the articles can be found by refer- 
ence to such bibliographic journals as the Index Medicus, The Index 


Catalogue of the Surgeon General's Office, and in particularly available 
form in the Quarterly Cumulative Index of the American Medical 
Association. Every effort has been made to give credit where it 
belongs ; if omissions or errors have been made they are due to the 
vast amount of material that has been accumulated on this subject 
rather than to intentional oversight. 

Our thanks are due to our colleague, Doctor Maurice L. 
Richardson, for extremely valuable aid in the revision of the manu- 
script, to Mr. E. L. Miller for three important microscopic draw- 
ings, to Miss May E. Treter and Miss Catherine E. Lennon for 
faithful and painstaking clerical work. Mr. W. T. Brownlow, of 
Cleveland, has made the line drawings and Mr. E. F. Faber, of 
Philadelphia, the drawings of the lungs in anaphylactic shock. We 
have taken materials from certain journals and make grateful 
acknowledgment by reference in the text. 

January, 1921. 














































1 . Apparatus for Filtration through Porcelain 43 

2. The Rosenau or Reichel Syringe for Injecting Toxin-antitoxin Mixtures. . . 47 

3. Wooden Box for Holding Rabbits 79 

4. Method of Obtaining Blood from the Rabbit's Ear 80 

5. Method of Complete Bleeding from the Femoral Vessels of the Rabbit. ... 81 

6. Collection of Serum in a Flask 82 

7. Method of Drawing Up Measured Volumes of Fluid into a Graduated Pipette 83 

8. The Wright Tube for Obtaining Small Quantities of Blood Serum 85 

9. Coiled Pipette for Taking Up Small Quantities of Fluids 85 

10. Microscopic Drawing of Bacterial Agglutination 84 

11. The Nipple Pipette : 96 

12. Hemolysis in the Test Tube 118 

13. Quantitative Relations of Amboceptor and Complement in Hemolysis 119 

14. Method of Obtaining Blood from Guinea-pig 128 

15. Stages of Lysis in Cholera Vibrios 144 

16. Microscopic Drawing of Phagocytosis 154 

17. Microscopic Drawing of Guinea-pig Lung in Anaphylactic Shock 214 

1 8. Blood-pressure Tracing from Dog in Anaphylactic Shock 216 


PLATE I. Positive Schick Reaction of Moderate Severity Seventy-two Hours 
After the Intracutaneous Injection of One-fortieth the Minimal 
Lethal Dose of Diphtheria Toxin. Patient's Blood Serum Was 

Found to Contain No Antitoxin 54 

PLATE II. Colored Drawing of Guinea-pig Lungs in Anaphylactic Shock 212 


THE history of immunology as a science is distinctly modern and 
in the investigation of details dates back only as far as the time of 
Louis Pasteur. Jenner's work on smallpox vaccination represents 
most painstaking and thorough investigation; it was epochal in 
character, and of the utmost importance in practical results, but was 
not immediately followed by any general application to other dis- 
eases, probably because of the limitations of technical methods. 
Observations of the phenomena of immunity were, however, made 
in ancient times and the resistance to second attacks of such dis- 
eases as measles, scarlatina, variola, varicella must have been com- 
mon knowledge from the earliest days of the human race. Whilst 
many of the earlier students of medicine recognized a certain simi- 
larity between poisoning and infectious disease, yet Hippocrates 
could see no such resemblance and his theory of the four humors 
was dominant throughout the Middle Ages. With minor exceptions 
this belief held sway until well into the Renaissance. In 1548, how- 
ever, Fracastore proposed the theory that infection was carried 
from person to person " per contactum " or " per fomites," and from 
this time dates real progress in the investigation of infectious dis- 
ease. This led subsequently to the establishment of two schools of 
thought, the one believing disease to be due to substances of basic 
or acid principle, and the other believing disease to be due to para- 
sites. The development of the latter idea was forced to await the 
discovery of means to view minute parasites and, as a matter of 
fact, was delayed much longer, because the invention of the micro- 
scope by Kircher in 1659 and van Leeuwenhoek in 1675 far ante- 
dated the connection now established between minute parasites and 
infectious disease. Nevertheless, Plenciz in 1762 expressed a belief 
in the direct etiological connection between certain forms of disease 
and microorganisms, and established the conception of the " con- 
tagium vivum." This idea was revived by Henle and by 
Brettoneau, but attracted no permanent attention. 

As perhaps the first observation leading up to our present con- 
ception of infectious diseases, and therefore to immunity against 
them, was the discovery in 1837 by Schwann that certain forms of 
fermentation are due to the presence of yeasts, an observation made 
at about the same time by Cagniard-Latour. Although at this time 
there was little, if any, thought that this discovery had any impor- 
tant bearing on infectious disease, yet within the succeeding decade 
favus, thrush, and pityriasis versicolor had been demonstrated to be 
due to specific fungi. Nevertheless, the possible similarity of fer- 
mentation and infectious disease had been considered in a more or 
less philosophical way, and Robert Boyle had said : " He that thor- 



oughly understands the nature of ferments and fermentations shall 
be much better able than he that ignores them to give a fair account 
of diverse phenomena of certain diseases (as well fevers as others), 
which will perhaps be never properly understood without an in- 
sight into the doctrine of fermentations." In the further develop- 
ment of the origin of infectious disease in living organisms perhaps 
the work of Rayer and Davaine on anthrax was of the utmost im- 
portance. They reported in 1850 that in the blood of anthrax vic- 
tims " are found little thread-like bodies about twice the length of a 
blood-corpuscle. These little bodies exhibit no spontaneous motion." 
In 1863 Davaine showed that the blood containing these rods could 
transmit the disease while blood free from them did not transmit 
the infectious agent. Davaine suggested at this time that the 
manifestations of the disease might represent the results of the 
specific fermentation produced by these bacilli. Such a parasitic concep- 
tion of disease was further supported by the discovery in 1873 of the 
spirillum of relapsing fever by Obermeier. Subsequently the work of 
Louis Pasteur, Koch, and the great school of early bacteriologists gave 
the final evidence in support of the " contagium vivum." 

Although the essential development of the science of immu- 
nology necessarily awaited the critical study of infectious disease, 
as can be seen from the foregoing summary of the development of 
the knowledge of the cause of infections, yet throughout the ages 
there had been speculations as to the nature of immunity running 
hand in hand with hypotheses as to the nature of infection. Im- 
munology took its most important step forward more than a half 
century before the work of Schwann had reached its fruition in the 
studies of Davaine, Obermeier, and Pasteur ; namely, in the master- 
ful experiments of Jenner. It is almost certain that for at least a 
century before Jenner's publication there had been practised, in the 
far and near East as well as in certain parts of Europe, including 
England, the inoculation of smallpox during full health in order to 
produce a mild attack of the disease and thus protect against later 
more severe or fatal attacks. It is indeed possible, as claimed by 
Carburi, that such a procedure originated in Europe as early as the 
sixteenth century and was carried to Constantinople and thence to 
the far East. Similar attempts to produce mild attacks of other 
diseases were tried, but with little success, as, for example, the work 
or Vesepremi in 1755 with plague, of Home in 1757 with measles, and 
of Turenne in 1844 with syphilis. It seems unlikely, however, that 
any of this work had any direct bearing on the discovery of Jenner. 
Sprengell states that for many years before Jenner's time the pro- 
tective influence of cowpox against smallpox was known in certain 
districts of Ireland, Holstein, Brandenburg, Switzerland, Catalonia, 
Peru, and the East Indies. Similar observations had been published, 
as, for example, the statement of Bose in 1769, that persons who 
had suffered cowpox were not subsequently attacked by smallpox. 
Jesty in 1774 had inoculated some members of his family with cow- 


pox and reported that they remained free from smallpox. In 1791 
Jensen and Plett practised protective inoculation with cowpox and 
reported good results, as did also Penster in 1765. None of these 
studies, however, bore critical scientific examination, nor did they 
serve to stimulate active work along this line. Indeed, it seems un- 
likely that they influenced Jenner in any way. Jenner brought to 
bear the critical method of the experimental investigator and proved 
the point. The method was rapidly put into clinical practice, 
spread over the British Isles and Europe and stood the test of 
time and wide application. With very slight modifications it stands 
to-day, in spite of our great advances in the study of immunity, as 
the most effective method we have to guard against infectious dis- 
ease. Jenner vaccinated a boy on the arm with cowpox virus ob- 
tained from a lesion on the hand of a dairy maid, and subsequently 
inoculated the boy with fresh smallpox virus, which failed to pro- 
duce the disease. He also reported an attempt to inoculate small- 
pox unsuccessfully in ten persons who had had cowpox nine 
months to fifty-three years previously. In 1800 Waterhouse in 
Boston repeated the experiment of Jenner on his own son, and in 
1802 performed a more extensive and even more critical experi- 
ment, in which he vaccinated nineteen boys with cowpox. Twelve 
were inoculated with smallpox virus three months later and failed 
to develop the disease, the same virus being inoculated at the same 
time into two unvaccinated boys, producing well-developed small- 
pox. The virus from these latter two boys was later inoculated into 
all the nineteen vaccinated boys without results. Thus began the 
period of experimental investigation of the phenomena of immunity. 
Further progress of importance was not made until 1880, when 
Pasteur announced his results in vaccination against chicken 
cholera. No brief review such as this can do justice to the stimulus 
to modern biological science furnished by this man and his asso- 
ciates, and the reader is referred to the interesting and intimate 
view of the life of Pasteur written by Valery Radot, his son-in-law. 
At the beginning of Pasteur's work the theory of spontaneous gen- 
eration was still generally accepted by the scientific world, and be- 
fore he was compelled to cease his active investigations not only 
had this theory been overthrown, but also the ideas of chemists in 
regard to crystallization and to the rotation of light by bodies in 
solution had been completely revised, the silk and wine industries 
of France, and indeed of the world, had been entirely rejuvenated, 
the bacteriological cause of numerous diseases conclusively proven, 
and the science of immunology put on a plane where its progress 
must be uninterrupted. His first contribution to the science of im- 
munology was in connection with his work on chicken cholera. 
Although he did not offer it as such, nevertheless, this incident well 
illustrated his doctrine that " chance favors the prepared mind." He 
had saved some old cultures of this bacterium and later found that 
they were avirulent. He subsequently tried to cause the disease in 


animals which had been inoculated with this virus, using the second 
time a culture which was virulent for untreated fowl. He showed 
that the inoculated fowl were immune to the virulent culture. In 
1881 he demonstrated with his collaborators, Chamberland and 
Roux, that this was not an isolated fact, but that essentially the 
same thing had been accomplished with anthrax. The virus of 
anthrax could not be attenuated by the same simple method as for 
fowl cholera, because the bacillus anthracis preserves its virulence 
by the formation of spores. They showed, however, that they could 
prevent the formation of spores by growing the bacillus at 42 to 
43 C. At this temperature growth of six to eight days sufficiently 
attenuates the organism for protective inoculation. The proof of 
the vaccination was given publicly before the Society of Agricul- 
ture at Melun. For this phenomenon Pasteur used the term vac- 
cination, and in London in 1881 said: " I have lent to the expression 
vaccination an extension that I hope "science will consecrate as a 
homage to the merit and immense services rendered to humanity 
by one of the greatest men of England Jenner." In 1882 Pasteur 
and Loir confirmed Thuillier's observations on the cause of swine 
fever and then successfully vaccinated pigs against this disease. 
Then in 1885-1886 came the final brilliant chapter in the work with 
rabies, in which vaccination was practised without definite knowl- 
edge of the etiological agent. The work with rabies was of further 
importance in that it led to the discovery of the fact that a virus 
may be increased in virulence, a phenomenon quite the reverse of 
the earlier discovery of the possibility of attenuation. 

In his studies Pasteur had worked almost entirely with the active 
organisms causing disease, and the next step forward was the dis- 
covery that the products of bacterial growth and activity can be 
utilized in the development of immunity. Salmon and Theobald 
Smith published in 1886 their studies on the immunization of hogs 
against hog cholera by the use of the products of the specific organ- 
isms. This idea had been suggested by LoefHer in 1884, but not 
proven. Before he had made any conclusive experiments the sub- 
ject had been taken up by numerous other investigators. Behring and 
Kitasato in 1890 had discovered tetanus toxin and Roux and Yersin in 
1888-1889-1890 had published their discovery of diphtheria toxin. 
These workers showed that the symptoms of the special diseases 
studied could be reproduced by the soluble products of the causative 
organisms and by their later work that one of the important phases of 
immunity is due to the development of substances capable of neu- 
tralizing these products. It became evident with further work that 
this principle does not apply to all pathogenic organisms, and the 
work of Pfeiffer with cholera in 1891 led to the differentiation of 
exotoxins and endotoxins. 

The antagonistic action of blood and body fluids on putrefaction 
had been noted by John Hunter, Traube, and Lister, but Grohman 
in 1884 was the first to publish well-founded experiments upon the 


inhibition by fresh plasma of the actual growth of bacteria. Fliigge 
and Nuttall in 1888 demonstrated under the microscope the destruc- 
tion of bacteria by blood, and Buchner in 1889 showed this property 
to be present in the serum. At about the same time the work of 
Richet and Hericourt and of Babes and Lepp showed that an 
immunity artificially produced against pyogenic cocci and against 
the virus of rabies could be transferred from one animal to another 
by means of the blood serum. These studies were followed almost 
immediately by the discoveries of Behring and Kitasato that the 
serum of animals immunized to the toxins of tetanus and of diph- 
theria bacilli not only could produce immunity in other animals, but 
that the specific disease could be cured by the use of the respective 
sera. These discoveries led immediately to the development of serum 
therapy, and in 1894 diphtheria antitoxin was being marketed in 
Germany. Contemporaneously with these developments Metchnikoff 
conducted his observations and experiments upon phagocytosis, and 
in 1883 published his " Recherches sur la digestion intracellulaire." 
He studied various lower forms of life, such as echinoderms, and 
found that during metamorphosis the atrophic cells of the larvae are 
devoured by other cells, either leucocytes or other phagocytic cells. 
These studies were later extended to include reparative conditions, 
such as the healing of wounds and resistance to infection. The out- 
come was a series of brilliant discoveries of the part phagocytosis 
plays in combating bacterial invasion, and ultimately the practical 
application in the use of bacterial vaccines for prevention and treat- 
ment of infectious disease. The discovery of the various forms of 
immune bodies and of the substances which might lead to the pro- 
duction of such immune bodies followed with considerable rapidity, 
but the details may best be left to the study of the particular immune 
bodies concerned, which include agglutinins and precipitins, cytoly- 
sins, and other complement binding substances. " That a plague 
of diarrhea in a poultry yard, studied by a professor of chemistry, 
should be the seed from which has grown the vast development of 
later years is a strange fact, but fact, nevertheless " (Adami). 









Mutual Relations of Host and Parasite. The existence of in- 
fectious disease depends fundamentally upon the invasion of a 
plant or animal by some infective agent. The infective agent is 
usually a microorganism either bacterial or protozoan in nature, 
although infestations by larger organisms, such as worms within 
the body or various forms of pediculi upon the surface, are some- 
times spoken of as infections. In addition to bacteria the vegetable 
world includes parasites, such as yeasts and fungi, which are cap- 
able of producing disease. The actual production of disease depends 
fundamentally upon the interrelationship between the infectious 
agent and the invaded body. Bacteria are widely distributed in 
nature, but the greater number of varieties have no capacity for the 
production of disease. Those which produce disease are spoken of 
as pathogenic, and those which do not produce disease are spoken 
of as non-pathogenic. There are forms, however, which although 
they ordinarily do not produce disease, may, under certain circum- 
stances, develop this character. Animals and plants possess cer- 
tain factors of resistance to the invasion of pathogenic organisms, 
and the pathogenic organisms possess certain characters which 
favor invasion. Both animals and plants live in constant associa- 
tion with microorganisms, and apparently in many instances both 
are benefited by this association. It is well known that certain 
plants require for favorable development the association of the nitri- 
fying bacteria. The intestinal canal of man, although free from 


bacteria in the first few days of extra-uterine life, soon becomes in- 
habited by large numbers of organisms, which produce no deleteri- 
ous effect under ordinary circumstances and, in fact, appear to aid 
in the process of digestion. Animals may adapt themselves to 
organisms even of the pathogenic varieties, as, for example, in the 
condition known as the " carrier state," in which virulent diphtheria 
bacilli or virulent typhoid bacilli are harbored without apparent 
harm. This capacity is due to certain changes which take 
place in the body, so that the organisms and their products do no 
damage. In the carrier state the organisms themselves have prob- 
ably developed a state of resistance against substances produced in 
the host which ordinarily would destroy the organisms and neu- 
tralize their toxic products. 

Parasitism. The parasite is a living organism which carries on 
its existence within or upon its host, an.d derives its nutrition there- 
from. Parasitic bacteria include both pathogenic and non-pathogenic 
forms. Bail has classified bacteria in three forms: (i) Pure sapro- 
phytes, which do not develop within living animal tissue, but derive 
nutrition from dead material ; these may be pathogenic, provided 
they produce poisonous substances which may be absorbed, as is 
the case with the bacillus aerogenes capsulatus; (2) pure parasites, 
which live entirely within tissues, including such organisms as the 
anthrax bacillus; they may exist in a vegetative form for long 
periods of time outside the body; (3) half parasites, which may be 
pathogenic if introduced into the animal body, but do not possess 
the invasive character and the necessity for life within tissues ex- 
hibited by the pure parasites. Most of the bacteria pathogenic for 
man belong in this last group, as, for example, the bacillus typhosus 
and the cholera vibrio. Such organisms as these may live and grow 
for long periods of time in water, and in foods of various kinds, may 
vegetate for a certain period under unfavorable conditions, but upon 
introduction into a susceptible host produce local lesions and in 
some instances may become moderately invasive for the entire 
organism. Symbiosis has relatively little significance in human 
medicine, but certain instances occur, as, for example, the apparent 
symbiosis of the fusiform bacillus and the spirillum of Vincent's 
angina. Certain parasitic protozoa, such as the endameba histolytica 
of dysentery, require the associated presence of bacteria, but these 
latter are not necessarily pathogenic and the phenomenon is not 
that of symbiosis, because the endamebse live at the expense of the 
bacteria, and the organisms, therefore, are not mutually advantage- 
ous to the existence of each other. 

Virulence. By the term virulence is indicated the capacity of 
an organism to produce disease. The degree of virulence may differ, 
not only between different species of organisms, but between strains 
within the same species. It is probably true also that individual 
organisms in the same culture possess different degrees of virulence. 
Furthermore, the virulence of a species or of a particular strain 


may be altered by favorable or unfavorable conditions. Virulence, 
however, does not depend entirely upon characters inherent in the 
infectious agent, because the production of disease is an exhibition 
of reaction between invading organism and host. We may, there- 
fore, say that virulence depends upon two groups of factors, those 
inherent in the invading organism and those dependent upon the 
resistance exhibited by the attacked individual. This resistance on 
the part of the host is represented by the condition of immunity and 
will be discussed subsequently. The capacity of the infecting organ- 
ism in the production of disease depends upon certain inherent ele- 
ments of virulence which are not well understood, upon the capacity 
of the organism to protect itself against the defensive mechanism of 
the host, upon the capacity to produce certain substances which aid 
invasion, and upon the development of poisonous bacterial products. 

Demonstration of Virulence. Inherent virulence of organisms 
may be demonstrated by the administration of accurately measured 
doses of the organism and observance of the effects upon susceptible 
animals. Ordinarily the dose is measured in the form of certain 
quantities of fluid culture. Growths on solid media may be meas- 
ured by the use of a platinum loop so standardized as to take up 
approximately 2 mg. of the organisms. Such growths may also be 
measured by suspension in a suitable menstruum. If 5.0 c.c. of salt 
solution are added to a slant agar culture, fractions of the resulting 
5.0 c.c. suspension contain equivalent fractions of the total surface 
growth. The most accurate method is that of Barber, who has developed 
a technic in which the use of a capillary tube permits picking a single 
organism out of a suspension. Of importance in considering viru- 
lence from this point of view is not only the quantity of organisms 
injected, but also the length of time they have lived upon artificial 
media, inasmuch as prolonged cultivation leads to deterioration of 
virulence. If a culture is maintained for a period of time without 
transplantation considerable numbers of the organisms die, and 
therefore may constitute a part of the bulk injected, at the expense 
of living organisms. This is not a true decrease of virulence and 
constitutes a factor of error. The route of injection is also of im- 
portance, because certain organisms may be virulent by one route 
of injection and not so by others. For example, the cholera vibrio 
may produce disease by introduction into the intestinal tract and is 
entirely without pathogenic effect when introduced subcutaneously. 

The Basis of Virulence. The studies of pathogenic bacteria have 
shown that they may acquire or in certain instances may lose viru- 
lence by passage through animals, and that they may lose virulence 
by cultivation upon artificial media. The method whereby they 
acquire virulence has been extensively studied. It is well known 
that the pneumococcus possesses a capsule when growing in ani- 
mal tissue, but that it loses its capsule after artificial cultivation. 
This is true of certain other organisms, and it has been demon- 
strated that the protection afforded by the capsule makes these 


organisms resistant to the defensive phenomena, phagocytosis and 
agglutination, as will be discussed in subsequent chapters. There- 
fore, capsule formation may well constitute an aid to invasion. 

Aggressins. It was found by Koch that tuberculous animals 
injected intraperitoneally with fresh cultures of tubercle bacilli suc- 
cumb soon after the injection, and that a considerable amount of 
exudate appears in the peritoneum. This phenomenon seems to 
have been the basis of Bail's aggressin theory. Bail injected tubercle 
bacilli, together with sterile tuberculous exudate, into healthy 
guinea-pigs and found that the injected animals died in the course 
of twenty-four hours, while control animals inoculated with the 
exudate alone did not show any appreciable effect, and control 
animals which received tubercle bacilli alone died only after the 
lapse of several weeks. He argued from this that the sterile exudate 
must contain a substance or substances which are responsible for the 
increased virulence or aggressiveness of the bacilli. He named this 
substance " aggressin " and believed that during an infection the 
organisms secrete certain substances which have power to inhibit 
or destroy the protective powers of the host. These bodies are sup- 
posed to be formed by the living bacteria in the living body only, 
and the pathogenicity of bacteria is said to depend, in part at least, 
upon their ability to produce aggressins. Bail believed further that 
the germicidal activity of body fluids in natural immunity had been 
overemphasized. He had noted with Petterson that animals highly 
susceptible to anthrax often possessed sera which had marked bac- 
tericidal powers against the anthrax bacillus. If such animals were 
inoculated with a few hundred organisms, a number easily destroyed 
by their sera, they nevertheless rapidly succumbed to the disease. 
Bail also showed that the peritoneal fluid of guinea-pigs dying after 
a fatal injection of typhoid or cholera organisms possessed the 
ability to increase the virulence or infectivity of particular strains 
that would otherwise have been harmless. Experiments of this 
kind were also performed in dysentery, chicken cholera, pneumonia, 
and staphylococcus infections, and the results obtained were identi- 
cal with those observed in the case of tubercle bacillus. Heating 
the exudate to 60 C. instead of inhibiting, increased the aggres- 
siveness of the organisms. Small doses appeared to act relatively 
more strongly than larger doses. In tuberculous animals the tissues 
seemed to be saturated with this body, and when fluid collected in 
the body cavities, as happens on injection of tubercle bacilli, these 
fluids contained large quantities of aggressins capable of inhibiting 
phagocytosis b^ preventing the migration of polymorphonuclear 
leucocytes. Bail, however, was not the first to observe this par- 
ticular phase of bacterial offense. Salmon and Smith, as early as 
1884, noted that bacteria multiply in the tissues of their host be- 
cause of a poisonous principle which is produced during their 
growth and multiplication. Kruse maintained that the organisms 
secrete ferment-like bodies (referred to as " lysins ") which have 


the power of inhibiting the bactericidal activity of the blood serum, 
thus allowing the invader opportunity for further invasion. By- re- 
peated injections of aggressin exudates into animals, Bail suc- 
ceeded in immunizing these animals against various infections, thus 
producing anti-aggressins. These rendered the bacteria defenseless 
and permitted unhindered phagocytosis. The agglutinative power 
of the sera of such animals was markedly enhanced. 

Wassermann and Citron, and many others, soon opposed Bail's 
aggressin hypothesis, by pointing out that the phenomenon can be 
explained without assuming that a new type of immune body is 
concerned. Wassermann and Citron, Wolff, Sauerbeck, and also 
Doerr found that the action of the so-called aggressins can be ex- 
plained by the fact that exudates contain extracts of the bacteria. 
Artificial aggressins were prepared by making extracts of bacteria 
in vitro. It thus seems probable that the aggressins are nothing 
more than endotoxins which have a negative chemotatic influence 
and a non-specific action. Citron was able to show by means of com- 
plement-fixation that the exudates contain free bacterial receptors, 
which by absorbing immune bodies, tend to neutralize the destruc- 
tive power of these antibodies. Levy and Fornet showed that fresh 
twenty-four- to forty-eight-hour culture filtrates of bacillus 
typhosus, paratyphosus, pyocyaneus and proteus possess non- 
specific aggressive powers and, according to Ikomikoff, aggressins 
of bacillus coli, staphylococci, and vibrios will act interchangeably, 
thus showing the non-specific nature of these substances. From 
Zinsser and Dwyer's experiments these bodies appear to be practi- 
cally identical with anaphylatoxins (see page 218). The addition of ana- 
phylatoxin to bacteria will change a sublethal dose into a lethal dose. 

Closely related to the aggressins are the " virulins " of Rosenow. 
This author found that freshly isolated cultures of pneumococci 
were not readily phagocyted, but this property was lost on repeated 
subculture. He prepared salt solution extracts of the virulent 
strains. Upon treating avirulent strains for twenty-four hours or 
more with these extracts, the avirulent organisms became virulent 
for animals, and at the same time resistant to phagocytosis. The 
substance contained in the salt solution extracts capable of render- 
ing the organisms virulent was named virulin. This substance ap- 
pears to be essentially the same as the aggressin prepared in vitro 
by Wassermann and Citron. In our opinion, these extracts, whether 
prepared in the form of exudates or as extracts, contain poisonous 
bodies which augment the invasiveness of the organism. They may 
be non-specific bacterial proteins or protein products, such as are 
probably contained in so-called anaphylatoxin. They may be 
in part endotoxins. The anti-aggressins of Bail are agglutina- 
tive and are probably called forth by the injection of the ex- 
tracted bacterial proteins in the exudates or extracts. It seems 
probable also that the effect of these anti-aggressins may depend 
upon their agglutinative capacity. The subject is confused and in- 


tricate, and whilst at present we are disposed to regard the aggressins 
as extracts of the bacterial proteins and their split products, as well, 
perhaps, as exotoxic in nature, further study may offer more com- 
plete and satisfactory explanation of the problem. 

Production of Poisonous Substances. -The virulence of organ- 
isms depends, to a certain extent, upon the poisonous substances which 
they produce. Nevertheless, virulence is not necessarily parallel to 
the capacity for production of these toxic substances. The poison- 
ous bacterial products may be divided into four groups, namely, the 
ptomains, which are the result of decomposition of the media upon 
which the bacteria grow ; the exotoxins or true toxins, which are 
soluble poisons produced by the life activities of the bacteria and 
easily absorbed and diffused in the body of the host ; the endotoxins, 
which develop within the bodies of the bacteria and are liberated 
probably only upon the death and disintegration of the bacteria ; and 
poisonous bacterial proteins, which result in large part from the break- 
ing down of the protein molecules which go to constitute the 
bacterial substance. 

The ptomains are formed from the decomposition of the media 
upon which bacteria grow, provided these media are nitrogenous in 
nature. The ptomains are basic substances formed not from the 
bacteria themselves, but from the decomposition products of those 
media which contain nitrogenous material, especially proteins whose 
nitrogen is in the form of amino-acids. Most ptomains are combina- 
tions simply of carbon, hydrogen, and nitrogen, and they may be 
divided into three groups, the first of which includes methylamine, 
dimethylamine, and trimethylamine ; the second group somewhat 
more complex, contains putrescin and cadavarin; the third group, 
the so-called cholin group, contains, in addition to cholin, neurin, 
muscarin, and betain. The cholin group are derivatives of lecithin. 
Cholin itself is found in extremely minute amounts in body cells and 
has a relatively low degree of toxicity. It is a substance which has 
been the subject of much experiment and hypothesis, but there is 
no very good reason for believing that it has any great pathologic 
importance. Neurin may be transformed from cholin, and although 
somewhat similar chemically, it is highly poisonous. Muscarin is a 
crystalline alkaloid obtained from poisonous mushrooms, but is also 
formed by the decomposition of fish; its chemical composition is 
very closely similar to that of neurin, and it may be prepared syn- 
thetically from cholin. Both neurin and muscarin produce definite 
toxic symptoms in man following subcutaneous injection of i to 3 
milligrams, but when given by mouth approximately ten times this 
amount are required, indicating that probably the liver breaks up 
and detoxifies that which is absorbed from the intestine. Betain is 
a constituent of plant tissues and has a toxicity from one-tenth to 
one-twentieth that of neurin and muscarin. The simpler ptomains 
are not extremely toxic. The ptomains as a group are not specific in 
any sense, except in so far as they are dependent on the chemical 


composition of the media upon which the bacteria grow, and any 
differences in constitution of ptomains are differences due to varia- 
tions in medium rather than variations of bacteria. In this respect 
they differ from toxins. Furthermore, it is not possible to produce 
immune substances against ptomains. Ptomains are not to be con- 
fused with toxins produced by bacillus botulinus, by bacillus enteri- 
ditis, or other members of the " food-poisoning " group, which are 
true toxins and are capable of inducing the formation of antitoxins. 
Food poisoning may, therefore, be due to the decomposition of food 
with the production of ptomains which are absorbed and produce 
toxic symptoms, or may be due to the presence in food of toxins 
produced by the bacillus botulinus and similar organisms. In addi- 
tion to the ptomains which contain C, H and N, a fourth group 
contains also oxygen, as exemplified in the substance sepsin ob- 
tained from decomposing yeast cells. This is closely related to 
cadavarin in its chemical composition and acts as a powerful dilator 
of intestinal capillary blood-vessels from which diapedesis may occur. 

The true toxins or exotoxins are soluble and diffusible poisonous 
substances produced by the life activity of bacteria. They may be 
produced when the organisms exist in a parasitic state or when they 
grow upon artificial media and the nature of a toxin for any given 
species is not determined by the medium upon which the organisms 
grow, except in so far as certain media favor the production of 
greater amounts of toxin than do others. The diphtheria bacillus 
produces the same toxin regardless of the medium upon which it is 
grown, although nutrient veal broth is the most favorable for toxin 
formation. The same general statement is true of the tetanus 
bacillus and those other organisms which produce toxins. Toxins 
are unlike ptomains in that they have not a definite chemical com- 
position and in that they serve to induce antitoxin formation. They 
have certain resemblances to enzymes, but are probably not identi- 
cal with enzymes. The nature of toxins, their action, and other 
details are considered in the chapter on toxins and antitoxins. 

The endoioxins develop within the bodies of bacteria and are not 
secreted into the surrounding medium. They apparently are only 
liberated upon the death and disintegration of the organisms. It is 
not certain that they can be differentiated absolutely from the 
poisonous bacterial proteins, and it is extremely difficult to induce 
antitoxin formation by their use. If they are injected into an ani- 
mal the animal may produce agglutinins and precipitins, but not 
antitoxin. This subject also is discussed subsequently. 

Poisonous Bacterial Proteins. The whole protein of certain 
bacteria is poisonous, and the work of Vaughan and Novy shows 
that the split products of bacterial proteins produced by treatment 
with alkalinized alcohol are extremely toxic. These substances 
apparently are not specific as regards the bacteria from which they 
originate, but owing to their poisonous properties they may add to 
the virulence of the organisms. Similarly toxic split products may 


be obtained from other proteins, such as those of cheese and milk. 
The poisonous effect is in some way connected with the foreign 
character of proteins. In some respects these substances resemble 
ptomains, but they are certainly not of the same constitution. They 
are obtained from bacteria regardless of whether these produce 
toxins, endotoxins, or ptomains, and are fatal for animals in very 
short periods of time. The methods for the production of endo- 
toxins are such as may lead to splitting of bacterial proteins, and at 
the present time no satisfactory differentiation can be made. The 
chapter on anaphylaxis and hypersusceptibility will present a dis- 
cussion of the poisonous substance called anaphylatoxin, which may 
also be related to the general group of poisonous split products. 
The influence of toxin on invasion by certain bacteria is illustrated 
by the recent work of Bullock and Cramer. They found that 
bacillus aerogenes capsulatus, vibrion septique, bacillus edematiens, 
and often bacillus tetani, when completely freed of toxin by washing 
or by heating to 80 C. for one-half hour do not produce the special 
disease upon injection into the rat or guinea-pig. The usual de- 
fenses of the animal, such as bacteriolysis and phagocytosis, are 
sufficient to rid it of the bacteria in the absence of toxins. A point 
of further interest in this work is the discovery that if a small dose 
of a soluble ionizable calcium salt be injected before or at the same 
time as the spores or toxin-free bacteria, the defenses are broken 
down and the special disease results. The experiments showed that 
this is not the result of action upon the bacteria, but is due rather 
to some influence upon the host. Bullock and Cramer suggest the 
name " cataphylaxis " for the rupture of defense. Other salts have 
no such effect, and it is possible to demonstrate the antagonistic 
action of magnesium upon calcium in similar experiments. It is 
difficult to find a series of experiments showing more clearly the 
delicacy of balance between resistance and infection. 

Alterations of Virulence Increase of Virulence. As has been 
indicated above, virulence may be increased by the passage of organ- 
isms through animals, and this method is commonly employed in 
laboratory work. The increase of virulence of the pneumococcus by 
passage through mice is an excellent example of the process. The 
organisms are injected intraperitoneally, recovered upon the death 
of the animal, cultivated for twenty-four hours, reinoculated, and the 
process repeated until a satisfactory degree of virulence is obtained. 
The degree of virulence is usually measured in terms of the bulk of 
broth culture which will kill an animal in a given period of time. 
In the case of some bacteria an increase of virulence by animal 
passage is only effective for the animal concerned; and the fact 
that an organism exhibits increased virulence for a guinea-pig does 
not necessarily presuppose that the same increase will apply to other 
animals. Not only is this true of direct animal passage but, as has 
been shown by Danysz, cultivation of an organism upon media con- 
taining rat tissue may increase the virulence for the rat but not for 


other animals. The importance of proper selection of the animal 
species for increasing bacterial virulence is emphasized by the work 
of Hussy, who found that the passage of streptococci through 
mammals and fish increased the virulence, but their passage through 
birds decreased the virulence. In the increase of virulence by means 
of animal passage, the organism apparently may develop a mechan- 
ism of resistance against the protective activity of the animal body, 
as has been discussed above. Another method of increasing virulence 
is to place the organism in collodion sacks. These are planted in 
the peritoneal cavity of an animal and apparently the slow diffu- 
sion of the animal fluids into the sack permits the organism to 
acquire resistance to the antagonistic substances of the animal and 
thus increases its virulence. A third method of increasing virulence 
is to grow organisms upon media which contain blood serum or 
other animal fluids. By several transfers upon such media the 
organisms may acquire resistance similar to that obtained in the 
other methods. A fourth method has been applied, depending upon 
the separation of the more virulent individuals in a culture from 
the less virulent at the height of phagocytosis. A culture is in- 
oculated into the peritoneal cavity of an animal, such as the guinea- 
pig, and by removing small quantities at regular intervals the time 
of greatest phagocytosis by the peritoneal cells is determined. The 
entire exudate is then withdrawn and slowly centrifuged, so as to 
throw down the cells, leaving the unphagocyted bacteria in the 
supernatant fluid. The organisms in the supernatant fluids are 
cultivated, and if they are not sufficiently virulent the process may 
be repeated until a satisfactory culture is obtained. 

Decrease of Virulence. The virulence of pathogenic organisms 
may be decreased by removing them from the favorable environ- 
ment of the animal host and growing them upon artificial culture 
media. As they become accustomed to this type of existence they 
usually lose considerably in virulence. As has been indicated above, 
there are instances where animal passage may decrease the virulence 
of certain infective agents. Whereas the virus of rabies increases 
up to a standard maximum on passage through rabbits, similar pas- 
sage through monkeys will decrease its virulence. It is probable, 
also, that the natural passage from dog to dog decreases virulence. 
It is now generally accepted that cowpox is the same disease as 
smallpox, yet the inoculation of cowpox into man produces a very 
mild form of disease. Therefore, it is to be presumed that the pas- 
sage of smallpox virus through the calf reduces the virulence. A 
similar example is found in the work of Hussy on the streptococcus 
quoted above. Decrease of virulence by animal passage is not 
clearly understood. It may be due to the same factors that influ- 
ence virulence in artificial culture media, whereby the organisms in 
an unfavorable environment lose their ability to combat the resist- 
ance of the animal host, or it may be due to a direct lowering of 
virulence as the result of more or less successful attacks of the pro- 


tective mechanism of the animal body. The influence of heat on the 
virulence of organisms is now well known. The degree of heat and 
the time of exposure must be so adjusted as to reduce virulence 
without causing actual death of the organisms. Similar reduction 
of virulence or attenuation may be accomplished by growing the 
organisms at temperatures which are not optimal. The first ex- 
ample of this was Pasteur's work in the attenuation of anthrax 
cultures by growth at 42 to 43 C. The attenuation by means of 
drying was practised in the classical work of Pasteur on rabies. 
The virus contained in the spinal cord of rabbits was subjected to 
desiccation, and it was found that the longer the time of desiccation 
the less potent was the virus. Chemical agents, such as phenol, 
acids, iodine and its salts, potassium bichromate, and others may 
also be used in proper concentrations and for proper periods of time 
to produce attenuation. Physical agencies, such as growth under 
pressure, the influence of light, etc., have been employed for pur- 
poses of attenuation. Of interest in connection with attenuation is 
the fact that certain organisms, when introduced into the body, vary 
in virulence, depending upon the route of introduction. For ex- 
ample, the virus of rabies may be injected intravenously into goats 
and sheep without producing rabies. This injection, however, serves 
to confer a certain degree of immunity upon the animals. As has 
been mentioned before, the organism of cholera may be injected 
subcutaneously without producing disease, and within certain limi- 
tations aids in the protection against invasion by these organisms 
through the intestinal canal. 







The Production of Infection. The widespread dissemination of 
bacteria in nature is such that they have ready access to plants and 
animals. Invasion by pathogenic forms may set up- infection. 
Whether or not the infection may lead to disease depends upon the 
final relationship established between the invader and the invaded 
body. There is probably no condition under which animals or 
plants fail to exhibit some degree of resistance to the invading 
organism, and similarly the latter attempts to accommodate itself 
to the conditions found in the invaded host. If the resistance be not 
sufficient to overcome the invader, infection results. The produc- 
tion of disease, however, depends upon the superior powers of the 
invader over the resistance of the host. Occasionally a mutual 
adaptation appears, under which circumstances an animal may be 
infected by an organism, but shows no symptom or sign of dis- 
ease. Not infrequently the trypanosoma Lewisi is found in the 
blood stream of rats, the rats continuing to live an apparently nor- 
mal existence. A similar mutual adaptation is found in the " carrier 
state," wherein man may harbor virulent diphtheria bacilli or other 
organisms without any evidence of disease. Mutual adaptation is 
not attained without a struggle on the part of both invader and 
host, and infectious disease results when the invading organism 
triumphs. This does not mean permanence of infection, because 
even although disease is established, the defenses of the host 
continue to operate, and often are augmented in such a way that 
ultimately the infection disappears. This accounts for the self- 
limitation of most of the acute infectious diseases. The increase in 
defensive powers may in certain diseases become permanent and 
immunity thereby be established. In all cases of recovery from 
acute infections immunity of some duration appears, although it may 
be limited to a few weeks or a few months. 

Entrance of the Invader. The entrance of the invading organ- 
ism may be due to an interruption of continuity of those surfaces of 
the body which ordinarily are impermeable to bacterial invasion. 
These surfaces include skin and the mucous membranes of the re- 
spiratory, alimentary, and genito-urinary tracts. The interruption 



of continuity may be due to trauma or may result from profuse 
growth of bacteria on the surface with the elaboration of poisonous 
products which may kill the epithelial cells. The former condition 
is exemplified in infected wounds and the latter in infection by 
diphtheria bacilli, streptococci, and fungi, such as produce favus, 
thrush, and pityriasis. Entrance may be favored by changes in the 
character of secretions, as, for example, the reduction of acidity of 
the gastric juice in certain forms of chronic gastritis. The bacteria 
may be implanted in some site which favors their multiplication, as, 
for example, in the crypts of the tonsils, in the crevices between 
unclean teeth and in hair follicles. Multiplication in these situa- 
tions favors the production of poisonous products which may by 
destruction of cells serve to interrupt surface continuity. Somewhat 
similar is the fact that extensive destruction of tissues may provide 
dead material in which saprophytes may develop, and if this mate- 
rial is so deep as to be excluded from the access of air, conditions 
favorable to the development of anaerobes are produced. Infec- 
tion may be favored by the movement of cells and fluids. For 
example, although leucocytes may take up bacteria, they do not 
invariably destroy them, and the migration of such leucocytes may 
lead to the dissemination of organisms by the subsequent death of 
the leucocyte. The movement of lymph may favor invasion as is 
seen not uncommonly in those cases of infections of the hand by 
streptococcus, wherein the lymph flow carries the organisms so as 
to set up infections of the lymph-vessels and the lymph-nodes, and 
even of the blood stream. Gaining access to the blood, the circula- 
tion of this fluid tissue may deposit bacteria in numerous foci 
throughout the body. The route of invasion depends somewhat 
upon the type of organism, those of typhoid fever, dysentery, 
and cholera, gaining access to the intestinal canal through the 
mouth. Their implantation upon the skin is of no significance, 
except that they may thence be transferred to the mouth. The 
gonococcus produces no lesions of the intestinal canal, but implanted 
in the genital tract, the eye, or the endocardium leads to serious 
results. If plague bacilli be inoculated subcutaneously in rats a 
large percentage of the animals survive, but if implanted in the 
lower respiratory tract small doses suffice to produce fatal infec- 
tions. The pneumococcus appears to infect man only through the 
respiratory tract. This phenomenon probably depends in part upon 
a local susceptibility to the organisms. 

Types of Infectious Disease. The types of infectious disease 
are differentiated according to the method of invasion and dissem- 
ination. An organism may grow locally and produce only local 
manifestations, as seen in a small abscess. It may grow locally and 
produce marked general disturbances, as is the case in diphtheria, in 
which instance, although organisms may enter the blood stream, 
they are usually confined to some focus, such as the tonsils. They 
elaborate in that situation poisonous substances which are absorbed 
and set up general manifestations of intoxication. Certain other 


diseases may produce marked local manifestations and rapidly in- 
vade the blood stream, as is true of typhoid fever. This organism 
enters the lymph-nodes of the intestinal tract, produces enlarge- 
ment, softening, and necrosis. The diarrhoea in these cases is largely 
if not wholly due to the local lesions, but the severe general mani- 
festations are due principally to the entrance of the organisms into 
the blood stream. Other diseases may show little local manifesta- 
tion, as is true of tetanus, but even with slight local disturbances 
profound general symptoms occur as the result of absorption of 
toxin. Other diseases, such as anthrax, may show little local mani- 
festation, but rapidly exhibit generalized infection through the blood 
stream. Infection then simply signifies successful invasion. Bac- 
teremia signifies the presence of organisms in the blood. Septicemia 
signifies blood infection associated with the production of toxic 
substances. Pyemia indicates that bacteria are present in the blood 
stream and because of lodgment in numerous situations produce 
multiple abscesses. Sapremia indicates absorption of toxic products 
from the growth of saprophytic organisms. Primary infections are 
those which occur without any decrease of resistance due to another 
infection. Secondary infections occur in individuals already suffer- 
ing from an infection of another nature. Such an infection is well 
exemplified in the secondary infection of a tuberculous cavity of the 
lung by staphylococcus. Terminal infections are those which occur 
near the fatal termination of some other disease, whether that other 
disease be of bacterial nature or of some other origin. Infections of 
this type are seen in the terminal broncho-pneumonias and sep- 
ticemias which occur in the course of certain chronic diseases. 
Mixed or multiple infections are not rare and it is sometimes diffi- 
cult to determine which infection is of greater importance. There is no 
doubt that one infection influences another existing at the same time and 
usually in a manner deleterious to the patient. Infection with measles or 
lobar pneumonia may excite latent tuberculosis into activity. Duke 
reports the lighting up of latent syphilis by an attack of typhoid 
fever and of latent gonorrhea by an attack of tonsillitis. The re- 
moval of one chronic infection may favorably influence another, as 
seen in the relief of certain cases of pyorrhea alveolaris by the re- 
moval of infected tonsils and in numerous other instances of mul- 
tiple chronic infections. 

Factors Favoring the Invader. The small size of pathogenic 
bacteria and protozoa aids in their avoidance of detection, favors 
transportation, and aids in penetration. The rapidity of multiplica- 
tion of such organisms is of considerable importance to their patho- 
genic powers. Those bacteria which form spores resist destructive 
agents and can resume activity when favorable conditions present. 
Certain of the protozoa, more particularly the endamebae, are cap- 
able of forming cysts which are more resistant to unfavorable en- 
vironment than the active organism. Either in the active state or 
in the vegetative state, organisms may persist for a long time in the 
so-called carriers, in intermediate hosts, or living as saprophytes. 


The microparasites, therefore, can be said to have a ready adapta- 
bility to varying environment and to be aided in propagation by 
their ability to derive nutrition from food-stuffs which possess 
wide differences in constitution. Certain bacteria apparently can 
produce their own protein from amino-acids and have no diffi- 
culty in deriving nutrition from whole proteins. As has previ- 
ously been indicated, those factors which go to increase virulence 
of organisms, such as capsule formation and the production of toxic 
substances, aid materially in invasion. 

Factors Inhibiting the Invader. Although rapid multiplication 
aids invasion, nevertheless, the brief life period which most of the 
microparasites exhibit is an influence operating against rather than 
in favor of invasion. Many pathogenic organisms are susceptible 
to the destructive influence of light, heat, desiccation, etc. In cer- 
tain instances the life of organisms outside an animal body operates 
to reduce virulence and therefore to inhibit the capacity for inva- 
sion and production of disease. 

Factors Operating Against Resistance. The animal host is sub- 
jected to the attacks of invading organisms because of the multi- 
plicity of contacts with the environment. The large body surface 
and locomotion of the body are influences favoring approximation 
of the invader. Certain living activities, such as the ingestion of 
foods and water, coitus, and the ready availability of superficial 
orifices, such as the nose, ears, mouth, anus, genital orifices, all aid 
invasion. The fact that most animals have a constant body tem- 
perature and that their tissues are continually moist, provides con- 
ditions favorable to the invading organism. Although light rays 
beyond the violet end of the spectrum have a certain capacity for 
the penetration of tissues, yet ordinary sunlight exhibits very little 
penetrability; therefore, the construction of the body is such that 
the inhibitory effect of light is not brought to bear upon organisms 
that have already gained entrance. The anatomy of the body pro- 
vides certain structures which are relatively inactive, such as the 
appendix vermiformis and the crypts of the tonsils where organ- 
isms find moisture, warmth, and darkness, suitable for their de- 
velopment. In chronic infections, particularly by the tubercle 
bacillus, necrotic tissues, or actual cavities may exist in contact with 
surfaces and with the outer air, and both conditions operate to re- 
duce resistance by providing favorable places for bacterial multipli- 
cation. The circulation of lymph and blood may operate against 
the host if organisms are particularly virulent. Inspiration of con- 
taminated air may also serve to aid invaders. The resistance of the 
host may, in a manner as yet unexplained, be decreased in general 
by bodily fatigue, exposure to heat and cold, poor hygienic sur- 
roundings, deleterious gases, or improper diet. The extremes of 
life, childhood and age, are associated with reduced resistance. 
Drugs, operative procedures, improper diet, and similar conditions 
favor infection. 

Factors Favoring the Host. The possession of intelligence by 


the higher forms of animal life aids in the detection and elimination 
of infective organisms. Not only may this be accomplished by .vol- 
untary movement, but the purposeful action of involuntary re- 
flexes may similarly aid the host. The body possesses a variety of 
defenses in the form of structure, secretions, chemical substances, 
cellular activity, all of which serve to aid in its protection in connec- 
tion with natural and acquired resistance to disease. These will be 
discussed in the next chapter. Plants produce certain diastases, 
aromatic products, aldehydes, and other substances which create in 
the plant a state deleterious to germination of harmful invaders. 
Pigments such as chlorophyl may destroy toxic substances and 
even bacteria in a manner somewhat similar to the action of 
bile pigment. 

The Course of Infectious Disease. The exact moment of inva- 
sion of an infectious agent is difficult to determine, but in cases of 
infectious disease, the time of exposure to infection can usually be 
stated to have occurred within the limits of a few hours. Following 
the moment of invasion there occurs a period of incubation during 
which the host exhibits no symptom of infection. This period of 
incubation in some diseases is extremely variable, whereas in others 
it is relatively fixed. In diphtheria incubation may apparently vary 
from twenty-four hours up to nine or ten days,, and certain other 
diseases show similar variation. In scarlet fever, on the other hand, 
the incubation period is very commonly five days, and numerous 
other diseases show similar fixity of incubation time. Following 
the period of incubation the less violent infectious diseases show a 
short period of prodromal symptoms in which headache, malaise, 
and other minor manifestations may appear. The next period, that 
of onset of disease or so-called invasion, may be frank or insidious. 
Lobar pneumonia may develop within a period of a few hours and 
exemplifies frank onset. As a contrast, typhoid fever is likely to 
occupy a week or ten days between the period of prodromal symp- 
toms and the full development of disease, thus illustrating insidious 
onset. That period during which the disease is at its height is called 
the fastigium or acme. Following the fastigium comes the period 
of decline or defervescence. This may be by crisis or lysis. Crisis 
is seen in approximately half the cases of lobar pneumonia, in 
which the decline occurs in a period of a few hours. Deferves- 
cence by lysis is seen in a large number of infectious diseases and is 
particularly well exemplified by typhoid fever in which several days, 
a week, or more, may be consumed. Convalescence indicates that 
period during which the symptoms of disease have practically dis- 
appeared and the patient gradually recovers and is restored to nor- 
mal. At any period the infection may become so overwhelming as 
to cause the death of the individual. Chronic infectious diseases 
exhibit no such regularity of development and decline. In con- 
trast to the acute infections, these are not likely to be self-limited, 
but progress until they have reached a point of such great severity, 
or of such complete exhaustion of the host that death ensues. 









Types of Immunity. Resistance to disease may be natural or 
acquired. If natural it may be of a species, race, family, or indi- 
vidual character. If acquired it may be naturally acquired, as seen 
in the immunity following an attack of infectious disease, or it may 
be artificially acquired. If artificially acquired it may be the result 
of active immunization or of passive immunization. Artificially 
acquired active immunity is such as may follow the injection of 
various antigens, such as toxins, bacteria, and numerous other sub- 
stances. Artificially acquired passive immunity is the result of 
transfer of active immunity from an immune animal to a normal 
animal, which latter becomes passively immunized. 

Natural Immunity. Although the term immunity may be consid- 
ered as equivalent to the capacity for resisting disease, nevertheless, 
in common usage it often implies an increase of resistance. In esti- 
mating an increase of resistance a normal degree must be presup- 
posed and the determination of the normal is extremely difficult. 
In considering natural immunity the term is used in contrast to sus- 
ceptibility and is not comparable to a normal level of resistance. 
Natural resistance to disease is favored by structure, movement, 
fluids, and secretions of the body. Structurally the skin is practi- 
cally impermeable to bacteria. In a general way this is true of 
mucous membranes, although we know that certain organisms may 
pass through mucous membranes of the intestinal tract without any 


lesions of the surface. Crypt-like structures, such as hair follicles, 
sweat glands, crypts of the tonsils, gastro-intestinal glands, urethra! 
glands, may serve as foci where bacteria are able to multiply, and 
may thus determine penetration by the organism. Accessory struc- 
tures of the skin, such as the hairs of the anterior nares and the 
cilia of certain parts of the respiratory tract, aid in either filtering 
the air or in propelling lodged organisms toward external orifices. 
The nature of certain secretions may be antagonistic to the growth 
of certain bacteria either by virtue of chemical substances, such as 
the hydrochloric acid of the gastric juice, normal alkali of the saliva 
and upper intestinal tract, or by virtue of digestive ferments which 
may act deleteriously upon bacterial growth. The movement of 
secretions, as, for example, that of the conjunctival sac, may favor 
the elimination of organisms. Bodily movement is of considerable 
value in resistance to infection, whether it be the simple process of 
wiping away irritating substances or the more intricate process of 
bathing either with water or with definite anti-bacterial fluids. Re- 
flexes such as coughing, sneezing, and vomiting are definitely pur- 
posive in protection. The movement of materials in the intestinal 
canal serves to prevent any too great bacterial activity, and if in 
spite of normal intestinal movement irritative substances are formed, 
the response by diarrhea serves a useful purpose in elimination. 
Internally the fluids of the body, more particularly the blood, con- 
tain definite anti-bacterial and anti-infective substances. In addi- 
tion to these the non-specific ferments of the body fluids aid in 
combating infection. The acidity or alkalinity of fluids within the 
body, as well as certain substances of unknown nature, may serve 
to retard or prevent bacterial invasion. Of great importance in pro- 
tection is the reaction of inflammation. In the course of this process 
fluids and cells are exuded from the vessels. The exudation of fluids 
upon surfaces aids in washing away bacteria, as, for example, the 
profuse exudation of fluid in acute coryza and acute enteritis. Accu- 
mulation of fluids may serve to dilute bacterial poisons and by diffu- 
sion and absorption aid in the elimination of these poisons. The 
cells which form part of the exudate possess, as characteristic func- 
tions, the capacity of taking up bacteria by phagocytosis and de- 
stroying them. The formation of fibrin in the exudate, as well as 
the subsequent proliferation of fixed tissue cells, serves to delimit 
the process and thereby aid in the prevention of widespread dis- 
semination of the organisms. In superficial inflammations the ex- 
foliation of diseased cells, as in scarlatina, may aid in the elimination 
of the infective virus. This does not mean, however, that such cells 
retain an infective character after long periods of desiccation. 

The physiological activity of cells in the body may be so excited 
as to aid in the elimination of toxic products, as exemplified by the 
early increase of activity in infectious disease. If the toxic mate- 
rial be sufficiently virulent this period of hyperactivity may be sue- 


ceeded by one of depression. The stimulation of cells in the produc- 
tion of antitoxic and anti-bacterial substances will be discussed sub- 

Classification of Natural Immunity Species Immunity. As has 
been indicated above, natural immunity may be found in species, 
races, families, or individuals. It is profitable to emphasize again 
that what we speak of as species immunity expresses a difference in sus- 
ceptibility exhibited by certain species as contrasted with others. 
Whereas man is susceptible to such diseases as syphilis, gonorrhea, 
cholera, and diphtheria, numerous other species are resistant to these 
diseases. It is possible to inoculate syphilis in higher apes, in the 
rabbit, possibly in the guinea-pig and other animals, but even suc- 
cessful inoculation shows a greater degree of resistance than is pos- 
sessed by man. Conversely, man is not susceptible to hog-cholera, 
chicken-cholera, rat-typhoid, and certain other diseases. Man is 
susceptible to the bacillus of human tuberculosis, but less so to 
that of bovine tuberculosis, still less to that of avian tuberculosis, 
and not at all to that of fish tuberculosis. In fact, with the exception 
of the rabbit, fish tuberculosis is not transferable to any of the warm- 
blooded animals-. Fish are not susceptible to human tuberculosis. 
Practically all animals are susceptible to snake venoms except the 
hog. Man is highly susceptible to pneumococcus and to bacillus 
pestis, but fowl are resistant to both these organisms. Metchnikoff 
showed that certain species of insects are susceptible to diphtheria 
toxin whilst others are not. Man is susceptible to trypanosoma gam- 
biense, but is resistant to trypanosoma naganse. In some instances 
these variations in susceptibility and resistance depend upon the 
environment. For example, frogs kept in low temperature are not 
susceptible to anthrax, but if kept in a temperature of 35 C. they 
succumb to the disease. Similarly it was found that if lizards are 
kept at 1 6 C. they could not be infected with plague, but at a higher 
temperature were susceptible. The work of Pasteur with anthrax 
in fowl is a classical experiment. He found that if he kept fowl at 
low temperatures they became susceptible to anthrax because of the 
decrease of body temperature ; but if they were allowed to maintain 
their normally high body temperature they were resistant. The 
temperature of most of the lower mammalia is higher than that of 
man, but the difference is not sufficiently great to explain all the varia- 
tions in susceptibility and resistance. 

Racial immunity probably exists but cannot be so conclusively 
proven in man as is true of species immunity. It is generally be- 
lieved that Caucasians are less susceptible to tuberculosis than 
negroes. That this is an inherent character of the race appears to be 
somewhat doubtful. Difference in hygienic conditions and in de- 
gree of exposure to the disease may account for much that appears 
to be racial susceptibility. It is possible that the superior hygienic 
conditions of whites in northern latitudes explains this difference. 
It is also possible that having been the victims of tuberculosis for 


many centuries a certain degree of racial immunity has been estab- 
lished by virtue of the elimination of more susceptible individuals 
and the survival of the more resistant. It is apparently true that 
when an infectious disease first attacks a race, it is more virulent 
than in those races where it is commonly found. The native African 
when brought into contact with tuberculosis appears to be attacked 
violently. The decimation of the population of Iceland after the 
introduction of measles was one of the horrors of improved com- 
munications; subsequent epidemics of the disease in the same people 
have been considerably less fatal. The introduction of syphilis into 
the American Indian showed a virulence unknown among the Cau- 
casians. Smallpox materially aided the Spaniard in his conquest of 
Mexico. The negro is supposed to be less susceptible to yellow 
fever than is the Caucasian, but careful investigation would make 
it appear that in infancy and childhood acquired immunity is estab- 
lished by mild attacks of the disease. The recent work of Love and 
Davenport shows that among 500,000 troops illness was 19 per cent, 
more frequent among negro than among white troops. The negro 
was apparently less resistant to pneumonia, tuberculosis, and small- 
pox than the white. The negro was more resistant to skin diseases, 
but contracted venereal disease readily and suffered more than the 
whites from extension and complications of venereal disease. Borell 
has reported that the Senegalese are very susceptible to pneumonia 
even in their own country. On transportation to France during the 
World War more than 5 per cent, succumbed to pneumonia before 
they had become acclimated, but in those who had been in France 
two or three years, the death-rate from pneumonia was much re- 
duced; only 2 in 7000 troops died of pneumonia. Whether this 
reduction is due to acclimatization or the early elimination of the 
more susceptible is an open question. An apparent racial immunity 
to malaria may be explained by the persistence of this disease for 
many years following a childhood infection. In Australia, New 
Zealand, and Tasmania during the years 1906-1908 there were only 
about half the deaths per thousand inhabitants as the result of tuber- 
culosis than occurred in Ireland, Norway, and Japan, during the same 
period; whilst the rate decreased regularly in the former countries 
it increased in the latter. This appears to favor the idea of racial 
differences of susceptibility, but a careful analysis of all the condi- 
tions may show that climate, mode of life, and hygienic conditions 
have a considerable influence. In the lower animals racial differ- 
ence may be more satisfactorily illustrated. Common sheep are sus- 
ceptible to anthrax, whereas the Algerian sheep seem to be immune. 
The culex mosquito rarely harbors the malarial parasite, whereas 
the anopheles are commonly infected. The field mouse is highly 
susceptible to glanders, whilst the white mouse is immune. The 
gray mouse is more resistant to streptococcus infections than is the 
white mouse. The common rat is more resistant to anthrax than 
is the white rat. 


Family Immunity. Members of certain families may through 
generations appear to be especially susceptible to such diseases as 
tuberculosis and rheumatism or the converse may be true. In the 
case of tuberculosis this difference may be the result of conforma- 
tion of the body. The physical character of flat, narrow chest and 
thin skin apparently go hand in hand with susceptibility to tuber- 
culosis, whereas the well-rounded chest appears to indicate resist- 
ance. In a family with whose history we are familiar the blondes 
have almost invariably succumbed to tuberculosis and the brunettes 
living under the same conditions and in intimate association have been 
resistant. This must be due to inherent constitutional characters and is 
not to be considered as a difference due to complexion alone. 

Individual Immunity. Variations of individual resistance or im- 
munity are seen frequently. It is true that the extremes of age 
show a certain proneness to infection and that this varies somewhat 
with individuals. Excellent examples of individual resistance are 
seen in great epidemics where some of those exposed apparently in 
the same manner and under the same hygienic conditions as others 
show either complete resistance to the disease, or, if they are at- 
tacked, develop only moderate or slight attacks. Infected water and 
foods consumed by a population may lead to disease in only a small 
portion of those exposed. Individual variations in animals are very 
frequent and offer a considerable source of error in the interpreta- 
tion of experimental results. If a series of guinea-pigs be injected 
with the same dose of anthrax bacilli, all will die at practically the 
same time, but if rabbits be treated in the same way some die 
within two days, others die subsequently, and still others are com- 
pletely resistant. On the other hand, rabbits are all susceptible to 
chicken-cholera, whereas the guinea-pig shows great individual dif- 
ference. Although a large number of children suffer from tonsillar 
infections, yet the incidence of acute articular rheumatism or of 
endocarditis is small and variable. Instances might be multiplied 
indefinitely of individual variations in resistance, but the phenom- 
enon is one of common knowledge. 

Inherited Immunity. The immunity transferred from parent to 
offspring may be a natural immunity or an immunity acquired by 
the parent. The transfer of natural immunity may be seen in racial, 
species, and family manifestations, and is probably a true transfer 
through the germ plasm. Congenital immunity may arise either in 
the form of an active immunity developed in the fetus because of 
the presence of antigens in the circulating blood of the mother, or 
may be in the form of passive immunity transferred from the blood 
of the mother to that of the fetus. It is conceivable that the fetus 
may survive an attack of disease transmitted from the mother and 
thereby become immune. It has been known since the time of 
Pasteur that certain dogs are immune to rabies. Remlinger has 
found that the guinea-pig may transfer rabies to the fetus and 
puppies have been known to become rabid several months after 


birth without any evidence of having been bitten, the disease there- 
fore probably having been contracted in utero. Immunity in dogs 
may be explained by direct transmission of immunity from the 
mother, or by survival of the disease in uterine or early post- 
uterine life. 

Acquired Immunity ^Naturally Acquired Immunity. The acqui- 
sition of immunity may be through so-called natural processes, such 
as passing through and recovering from an infectious disease, or it 
may be induced and artificially acquired by special methods of im- 
munization to be described. In both these instances, although the 
normal level of resistance cannot always be accurately determined, 
yet there is no doubt that the acquired immunity represents a higher 
level of resistance than is normally possessed. For example, the 
fact that when a patient has survived an attack of such a disease as 
scarlatina and then in spite of repeated and intimate exposure re- 
sists infection, leaves no doubt that his acquired immunity repre- 
sents a higher level of resistance than he possessed before the attack 
of the disease. The diseases which confer a lasting immunity include 
acute anterior poliomyelitis, chickenpox, cholera, epidemic cerebro- 
spinal meningitis, measles, mumps, plague, scarlatina, smallpox, 
typhoid fever, typhus fever, whooping-cough, and yellow fever. 
The question as to whether or not syphilis confers a lasting im- 
munity has been reopened by the discovery of the Wassermann test 
and by the work of Warthin. The Wassermann test has shown that 
many cases of apparently cured syphilis are really in a latent stage 
of the disease. Warthin has found the treponema pallidum in 
various organs at autopsy on syphilitics who clinically appeared to 
be free from the disease. If Warthin's work can be confirmed in a 
large number of cases it would appear that syphilitic infection re- 
mains latent throughout the life of the individual in the vast ma- 
jority of cases, even in spite of the fact that the Wassermann test is 
negative and no clinical signs of the disease are demonstrable. If 
syphilis be curable, the reported occurrence of second infections in a 
small number of instances would make it appear that any immunity 
which may develop is not permanent. The long duration of the 
disease would account for the small number of reinfections reported. 
Immunity in tuberculosis has been extensively studied, and as yet 
no final and conclusive statements can be made. It seems probable 
that tuberculosis is never completely eliminated from the body, and 
although the patient exhibits no symptom nor sign, he still may 
harbor the disease. The studies of Opie and others would make it 
appear that the development of tuberculosis in adult life is traceable 
directly to old lesions which occurred in childhood. The fact that a 
very large number of individuals show at autopsy small lesions indi- 
cates the prevalence of the disease. Subsequent active development, 
following encapsulation of a lesion, appears to be due to certain fac- 
tors which either reduce the protective properties of the body or 
excite the organisms to renewed activity, or both. 


Artificially Acquired Immunity. The artificial acquisition of im- 
munity may be the result of active development of immune sub- 
stances in the organism or it may be due to the transfer into the 
organism of immune substances from an immune animal. Arti- 
ficially acquired immunity differs from naturally acquired immunity 
in that it is likely to be less durable. If acquired by active immuniza- 
tion the duration is likely to be considerably greater than if acquired 
by passive immunization. In the discussion of immunity it is well 
to keep clearly in mind the definition of antigen and antibody. The 
antigen is a substance which upon introduction into the body in 
proper amounts and under suitable conditions induces the formation 
of a special antagonistic substance, the antibody. Conversely the 
antibody is the substance produced as a result of the introduction 
of antigen. Experimentally the antigen is usually introduced by 
parenteral routes, meaning routes other than by way of the ali- 
mentary canal, such as intravenous, intraperitoneal, subcutaneous, 
intrathecal, intraocular, and by other similar pathways. The nature 
of antigens and antibodies will be discussed in the subsequent chap- 
ters, but it may be said here that both are of protein nature. Every 
soluble complete protein, with the exception of the racemized pro- 
tein of Dakin, may serve in at least some degree as an antigen. 
The proteins employed are for the most part native, but synthetic 
proteins may also act as antigens. Wells states that " of the cleav- 
age products of proteins it is certain that none of the amino-acids 
and simple polypeptids can act as antigens, and it is not yet fully 
established that even such large complexes as the proteoses are 
antigenic, although there is some evidence in favor of this view." 
There have been numerous reports of the use of lipoids as antigens, 
but this relation has not been definitely established. If lipoids are 
obtained from animal tissues favorable results may be obtained, but 
in none of these experiments is it proven that the lipoids are entirely 
free from proteins. Ford has successfully employed a hemolytic 
glucoside obtained from the poisonous mushroom amanita phalloides 
as an antigen for the production of an anti-hemolysin, but this is 
the only well-established exception to the general rule that antigens 
are of protein nature. 

Actively Acquired Immunity. This may be produced by actual 
infection of an individual during a period of good health by the 
virus of the disease to which he is to be immunized. The classical 
example of this form of immunization was the practice for many 
centuries of inoculating smallpox into the healthy, so as to induce 
a mild attack of the disease. The danger lies in the uncertainty 
of action of the virus, since apparent health does not necessarily 
presuppose resistance to any special disease. If the virus can be 
measured in some way so that an extremely small amount can be 
inoculated, the procedure is somewhat safer. Protection against Texas 
fever in cattle has been practised by permitting nursing calves to be 


bitten by a small number of infected ticks or by injecting intraven- 
ously a small amount of blood from an infected animal. 

Somewhat similar to the above examples is infection with attenu- 
ated virus. Such attenuation may be obtained by prolonged cultiva- 
tion on artificial media, by heat, by passage through animals, by 
desiccation, by the use of chemical agents, and by pressure. If heat 
be employed for attenuation, rather than for killing the organisms, 
it must be properly adjusted. Toussaint employed this method in 
his early experiments with anthrax in which he heated infected 
blood to 55 C. for ten minutes. This method, however, is not re- 
liable, probably because of variations in the resistance of individual 
members of a culture of any given organism. Heat may be applied 
also during the cultivation of organisms upon artificial media, a 
method practised by Pasteur in producing anthrax vaccine. The 
heat must be of such a degree as to permit growth of the organisms, 
but at the same time reduce the virulence. As has been pointed 
out before, the cultivation of organisms upon artificial media through 
many generations leads to a reduction of virulence. This latter 
method was employed by Pasteur in the development of the vaccine 
for chicken-cholera. The attenuation of smallpox virus by passage 
through the calf so reduces virulence that the virus may safely be 
inoculated into man. Pasteur found that the virus of swine ery- 
sipelas could be attenuated by passage through rabbits, and it is 
well known that the passage of rabies virus through dogs and 
through monkeys reduces its virulence. An excellent example of 
attenuation by desiccation is found in the preparation of anti-rabic 
vaccine. For this purpose the virus is raised by passage through 
rabbits to a standard degree of virulence, the " virus fixe." The 
spinal cord of a rabbit so infected is desiccated at 25 C. over KOH. 
This method of attenuation is so delicate that there are distinct 
variations in virulence between fragments dried for five, six, and 
seven days, as well as virus dried for thirty-five, thirty-six, and 
thirty-seven days or intervening periods. The longer the desicca- 
tion the greater the reduction of virulence and the greater the safety 
of the inoculation. Attenuation by the use of chemicals, such as 
phenol, potassium bichromate, and sulphuric acid, has been prac- 
tised. Chemical attenuation may also be applied to toxins, as in the 
use of iodine terchloride and potassium iodide. A pressure of eight 
atmospheres at a temperature of 28 to 39 C. has been employed 
for the attenuation of anthrax cultures, but is probably not widely 
applicable, is difficult, and possesses no superior advantages. 

Immunization with Dead Bacteria. In the study of immune 
processes it was finally found that killed bacteria could be used for the 
production of immunity. The organisms may be killed by heat or 
by chemicals. In either case, it is necessary so to apply these agents 
as to kill the organisms without destroying their proteins. The 
use of heat sufficiently high to destroy spores leads to destruction 
also of the proteins, and therefore the method does not apply to 


spore-bearing organisms. Those organisms which do not produce 
spores can be killed by heat of 58 to 60 C. for thirty .to sixty 
minutes, and this degree of heat does not alter the character of the 
proteins. The chemicals most frequently employed for killing bac- 
teria so as not to alter the proteins are formaldehyde and phenol. 

Immunization with Bacterial Products. In addition to the use 
of dead bacteria, as indicated above, it has been found possible to 
produce immune reactions by the use of extracts of the organisms, 
these extracts containing a considerable amount of bacterial pro- 
tein. Immunization of this sort leads to the formation of anti- 
bacterial sera which agglutinate the bacteria or precipitate bacterial 
extracts. It is possible also that this method of immunization leads 
to the formation of other immune substances. How far protein, 
either in solution or in the bodies of bacteria, may be broken down 
and still be capable of leading to the formation of immune bodies is a 
question that has been extensively studied. Certainly any change 
that breaks up the protein into its fundamental amino-acids is likely 
to destroy its antigenic properties. Simple fractionation by means 
of salting still leaves sufficient native protein to serve to immunize. 

Of bacterial products which have been employed for immuniza- 
tion none is more important than those poisonous bodies called 
toxins. In the classification of toxins we have referred to the true 
toxins or exotoxins and to the endotoxins. There is little support 
for the belief that endotoxins as such, except in rare instances, can 
produce immune substances. On the other hand, the production of 
a neutralizing antitoxin against the exotoxins has constituted one 
of the most brilliant chapters in the study of immunology, and it 
will be given discussion in the chapter on toxins and antitoxins. 
The use of toxins as antigens involves the employment of these 
substances in non-fatal doses, their attenuation by chemical and 
physical means, or their primary neutralization by means of previ- 
ously prepared antitoxins. In experimental work on animals the 
first two methods are commonly employed and may be combined 
with the third method. In man immunization by the use of toxins 
is practised mainly in connection with active immunization to diph- 
theria. The combination between toxin and antitoxin is not in the 
nature of a fixed and final reaction, and under certain circumstances 
partial dissociation may occur. The active immunization of man 
by the use of neutralized mixtures of toxin and antitoxin appears 
to provide conditions whereby dissociation progresses gradually, 
and the toxin is liberated in such small amounts that it does no 
harm and yet induces in the body antitoxin formation. In the mean- 
time the individual is protected by the antitoxin simultaneously 
dissociated. Recent studies make it appear that several organisms 
which formerly were supposed to produce only endotoxins elab- 
orate in addition true toxins, and some of the earlier studies sup- 
porting the assumption that antitoxins could be produced by these 


endotoxins are probably fallacious, because of the mixture of un- 
recognized exotoxins, the latter producing the immune reaction. 

Active immunization may be produced not only by toxic sub- 
stances elaborated by bacteria, but also by toxic substances produced 
in animal life, such as snake venoms, spider poisons, and similar 
substances. Higher plant poisons, such as ricin, abrin, crotin, etc., 
may produce specific neutralizing antibodies. The practical value 
of the antitoxins prepared against bacterial toxins and against the 
venoms produced by animals is such as to have added greatly to the 
combating of poisoning by these substances. 

Passive Immunization. In active immunization the animal 
manufactures within its own body immune substances which serve 
to protect against and combat infection. Passive immunization, 
however, utilizes these immune substances, through the transfer of 
blood serum containing the products of active immunization. The 
most common example of passive immunization is found in the 
therapeutic use of diphtheria antitoxin. For practical purposes the 
diphtheria antitoxin is manufactured in the body of the horse. The 
injection of immune horse serum transfers to man the immunity 
actively produced in the horse. Passive immunity of this sort serves 
to protect against infection, and until the possibility of active im- 
munization of man against diphtheria was demonstrated, the former 
method was widely employed for protection of exposed individuals 
against diphtheria. This method of protection has the great advan- 
tage of quickly conferring immunity and is widely employed when 
time does not permit the use of methods for developing active im- 
munity. After the disease has developed the use of immune serum 
to combat the infection has the utmost value. In the case of tetanus 
antitoxin the protective value of prophylactic injections has been 
amply demonstrated, but in this instance the great affinity between 
nerve tissues and tetanus antitoxin is such that the therapeutic use 
of tetanus antitoxin after the disease has developed has not given 
such beautiful results as has been true of the serum treatment of 
diphtheria. Much encouragement has recently been afforded by the 
use of similarly prepared antitoxins against the toxin of the bacillus 
of gas-gangrene, and there is little doubt that the methods may be 
much more widely employed as it becomes possible to demonstrate 
the formation of true exotoxins by other bacteria. Not only may 
advantage be taken of substances produced by artifically acquired 
immunity, but in certain instances it is feasible to use the blood 
serum of individuals who have acquired immunity by survival of an 
attack of certain diseases. In this field, however, the facts have not 
been accumulated in sufficient number to justify unqualified ap- 
proval of the method. 

Passive immunity may be not only antitoxic in character, but 
also anti-bacterial. Anti-bacterial immune sera have been prepared 
against the streptococcus, the meningococcus, the pneumococcus, 
and other organisms. The success with passive immunization by 


the use of these sera has not always been so clear cut as in the case 
of antitoxic sera. Nevertheless the use of anti-meningococcus sera 
has reduced the mortality of epidemic cerebrospinal meningitis from 
75 or 80 per cent, down to 35 or 40 per cent, or lower. The results 
with anti-streptococcus sera have been variable. Although the 
early reports of the use of anti-pneumococcus sera were highly en- 
couraging, later study has thrown some doubt upon the value of 
this method of treatment. Much further study of the subject is re- 
quired before a definite conclusion can be reached. 

Theories of the Nature of Immunity. In the early study of im- 
munity numerous hypotheses were advanced as to the action and 
development of immune bodies. It was known, for example, that 
when bacteria are grown for a long time upon a culture medium 
certain substances are produced which have a deleterious influence 
upon the further growth of the organisms and may actually lead to 
their death. It was easy to assume, therefore, that recovery from 
an infectious disease might be due to the development of similar 
antagonistic substances within the infected host. Another theory 
was to the effect that bacteria growing in the body utilize and 
exhaust the specific nutritive substances necessary for their growth 
and then die. It was also thought that the death of bacteria in the 
body was due to changes in reaction of the blood, and further that 
altered osmotic conditions changed the permeability of cell mem- 
branes so as to permit ready entrance of poisonous substances. 
These theories, however, could not withstand the demonstration of 
passive transfer of immunity, the production of immunity by the 
use of killed organisms, or perhaps more important, the clear demonstra- 
tion of immune reactions in vitro. 

The Ehrlich Side-chain Theory. As more and more facts were 
added to the knowledge of the subject, Ehrlich propounded his side- 
chain theory. This was based upon the law of Weigert, which 
states that when animal cells are required to repair an injury 
they not infrequently exceed the absolute necessity for repair and 
produce tissue in excess. Ehrlich, therefore, hypothesized that the 
injurious substances of infection demand of the cells the forma- 
tion of protective bodies, and that the cells respond to this demand 
in such excess that the protective bodies are formed in amounts not 
only sufficient to meet the requirements, but in such excess as to free 
circulating immune substances in the blood. This hypothesis in- 
troduced an entirely new terminology into the subject. It was 
supposed that cells normally possess certain specific receptors or 
combining groups for the injurious substances much as a struc- 
tural chemical formula exhibits free valencies on the part of certain 
elements or groups. When all these combining groups of the cell 
are utilized and uncombined poisonous material exists in the circula- 
tion, the cell produces and liberates additional receptors even in 
excess of demand. These free receptors constitute the circulating 
immune substances. The study of immune substance demon- 


strates somewhat variable activities. For example, it was found 
that antitoxins operate differently from other immune substances; 
that agglutinins and precipitins operate in a special fashion which 
is practically identical for both substances; and that cytolysins, includ- 
ing the lytic bodies for bacteria as well as for animal cells, require 
the presence of fresh serum containing the so-called complement or 
alexin. The specific cytolysins were found to be similar to certain 
other substances which are now referred to as complement-fixing 
bodies. Finally the discovery of opsonins and tropins showed that 
there is in all probability a fourth group or sub-group of these 
immune substances. 

The Ehrlich Classification. Ehrlich, on the basis of the general 
outline given above, divided the immune bodies into three groups, 
depending upon demonstrable differences in their nature. He found 
that the receptors in some instances are not immunologically simple 
bodies, but that even in this sense they show varying degrees of 
complexity. In the more complex forms the actual receptor or 
combining groups constitute only a part of the immune substances, 
and he therefore applied a more comprehensive term, the haptines. 
He included in the haptines of the first order the antitoxins, in the 
haptines of the second order the agglutinins and precipitins, and in 
the haptines of the third order the cytolysins and other amboceptors. 
The early studies of antitoxins made it appear that the neutralizing 
effect of these substances was similar to the neutralizing action of 
alkalies and acids, but it was subsequently discovered that such 
combinations may be, at least in part, dissociated. It was then 
found that toxin may undergo a variety of changes as the result of 
preservation. Subsequently it was learned that the antitoxin would 
combine not only with the toxin, but with its degeneration products. 
This has complicated the conception considerably, and we may say 
in brief that according to the Ehrlich conception the antitoxin con- 
stitutes a simple receptor or combining group capable of entering 
into combination with a special combining group in the toxin called 
the haptophore. In order to account for the combination of anti- 
toxin with the degeneration products of toxins it was necessary to 
assume that the toxin exhibits its essential combining property in 
the haptophore group and that the toxin also possesses a toxophore 
group, serving to give it its poisonous character and partly de- 
stroyed during preservation or by certain degrees of heat. The 
second category of Ehrlich includes the agglutinins and precipitins. 
In the study of these substances it was found that the agglutinins 
and precipitins may be deprived of the agglutinating and precipitat- 
ing properties by preservation or by the application of certain de- 
grees of heat. Ehrlich, therefore, conceived the idea that in this 
instance we have to deal with a somewhat more complicated haptine 
containing a combining group and a so-called zymophore group, 
the latter leading to the special reaction. These constitute the re- 
ceptors or haptines of the second order. This assumption is neces- 


sary, because even although the agglutinating and precipitating 
properties are destroyed by heat or other means, nevertheless, there 
remains a group capable of entering into combination with the anti- 
genie substances, so that the addition of a complete agglutinin or 
precipitin produces no effect. The third category of Ehrlich includes 
the receptor or haptine which has been named by Ehrlich the ambo- 
ceptor, and by Bordet the sensitizer. In this instance the receptor 
produced by the cell is conceived as a body possessing two com- 
bining groups, one serving to combine with the antigen and the 
other serving to combine with complement. These two groups have 
been called the cytophilic group and the complementophilic group. 
The complement is a thermolabile substance which has little or no 
capacity for combining with the antigen. Accepting Ehrlich's hy- 
pothesis, this haptine of the third order constitutes an intermediary 
body through the action of which the complement is brought into 
contact with the cells, be they bacterial or animal, so as to lead to 
solution. Bordet, however, believes that the immune body enters 
directly into combination with the antigen, thereby " sensitizing " 
it so that the complex is operated upon by the complement, or as he 
calls it, the alexin. The discovery of the phenomenon of comple- 
ment-fixation demonstrated that a similar substance may operate in 
the presence of dissolved protein and complement, so as to engage 
the complement in such a fashion that it is not available for other 
reactions. In these reactions the participation of the complement is 
an essential and necessary condition of the reaction. The original 
Ehrlich theory could not consider the subsequently discovered 
opsonin or tropin. This substance prepares bacteria and other 
cells for phagocytosis. It was at first supposed to be a simple 
immune substance, but as the study of its activity progressed it was 
found that the presence of complement increases its activity, al- 
though this latter body is not essential and necessary. We, there- 
fore, propose to consider the opsonin as belonging essentially to the 
haptines of the third order. The way in which this differs from the 
original haptine of the third order is simply in the fact that com- 
plement may or may not be utilized in the reaction. In order to 
differentiate we suggest that the amboceptors of Ehrlich be looked 
upon as " obligate " amboceptors and the opsonin be regarded as a 
" facultative " amboceptor. 

Recent Criticism of the Ehrlich Hypothesis. Following the 
earlier discoveries of immune phenomena numerous studies were 
made of the chemistry of immune substances and immune reactions. 
These will be discussed in the chapters on the special immune reac- 
tions. It may be said at this time that many objections have been 
raised to the Ehrlich hypothesis, particularly as the study of physi- 
cal chemistry, more particularly that part which refers to colloids, 
has advanced. As will be seen from the brief review of the Ehrlich 
hypothesis given above, this investigator was much influenced by 
the status of chemistry which prevailed when he announced his 


views. The idea predominated that the immune reactions resemble 
the more or less fixed changes which are seen in the chemical reac- 
tions of crystalloids. As it was found that practically all immune 
substances are colloidal in nature and either are proteins or are very 
closely related to proteins the similarity of the immune reactions to 
colloidal reactions became more and more strongly emphasized. In 
fact, in a general way, practically all immune reactions parallel in 
their general phases similar demonstrable reactions with colloids. 
There is but one feature of immune reactions which has not yet 
been explained on the basis of colloid chemistry, namely, their 
specificity. This does not mean, however, that further investiga- 
tion will not clear up this phase of the problem. It is but fair to say 
that the Ehrlich hypothesis provides an excellent basis for the classi- 
fication of immune phenomena, but as will be shown subsequently, 
the conception underlying the Ehrlich hypothesis is not adapted to 
the more modern views of the mechanism of immune reactions. The 
combination of toxin and antitoxin shows numerous features not to 
be explained by the simpler reactions of crystalloids. The same is 
true of agglutination, precipitation, cytolysis, complement-fixation, 
and anaphylaxis. 

Specificity of Immune Reactions. The antitoxin elaborated in 
the response to injections of diphtheria toxin or to the presence of 
the disease itself is a substance which reacts only with diphtheria 
toxin. The agglutinins and precipitins produced by injection of 
bacteria and of dissolved proteins act most powerfully upon the sub- 
stances used for injection. In this case, however, these immune 
bodies may also react less strongly with other closely related bac^ 
teria or proteins. Cytolysins induced by the injection of certain 
cells react strongly with those cells, but also less strongly with 
closely related cells. This phenomenon of reaction with closely re- 
lated bodies is spoken of as the group phenomenon and may be 
exhibited also in connection with complement fixation and ana- 
phylaxis. Even where purified proteins are employed the same 
phenomenon may be observed. In spite of the group reaction, how- 
ever, the immune substances are most highly specific for their spe- 
cial antigens. Specificity has been employed for the detection of 
particular proteins of animal species, of bacterial species, and it 
has lent support to the Darwinian theory of species relationship and 
evolution. Much thought and study has been given to the resem- 
blance between immune substances and enzymes, but in no sense 
can enzymes be said to have the same specific character as immune 
bodies. There is no satisfactory explanation of specificity. Why 
the injection of red blood-corpuscles of the sheep should induce the 
formation of a hemolysin capable of dissolving the red cells of the 
sheep but not of other animals, except in minor degree of those 
closely related to the sheep, cannot be explained. As can readily be 
understood, specificity involves the use of special antigens and the 
formation of more or less specific immune substances. The wide 


range of possibility in this connection is indicated in the building- 
stone theory of Abderhalden. Bearing in mind that practically all 
immune substances are protein in nature and that proteins are made 
up of numerous amino-acids, Abderhalden calculated that twenty 
amino-acids could be so combined as to form 2,432,902,008,176,640,000 
different compounds. He illustrates this possibility by stating that 
if three amino-acids are building stones which may be designated 
A, B, and C, they can be grouped together so as to form six different 
combinations, ABC, ACB, BCA, BAC, CAB, and CBA, and that 
four building stones can form twenty-six such combinations and so 
on until the enormous possibility of different combinations of 
twenty amino-acids is reached, as illustrated in the figures given 
above. Chemically no such enormous number of proteins is known, 
but if immune specificity could be shown to depend upon slight 
differences of molecular arrangement, Abderhalden's figures indi- 
cate the number of immunologically specific proteins obtainable. 
Taking for granted the phenomenon of specificity, that of the group 
reactions can be more readily explained. In this case it is assumed 
that in the proteins of closely related species there is some group of 
molecules common to these species, and further that the formation 
of immune substances in response to injections of this common 
group leads to the production of a substance which may react with 
the common group. In each species, however, there is in addition 
to the common group special groups which determine the specificity 
of the substance as an antigen as well as the production of an im- 
mune substance with a higher degree of affinity for the combined 
groups of the particular species than for the common group. 

Non-specific Therapy of Infectious Disease. As a result of the 
extensive studies of infectious disease various modes of treatment 
have been elaborated. It is well understood that the organism 
offers resistance to these infections and that the support of circula- 
tion and excretion by simpler pharmacological methods aids mate- 
rially in the treatment. Not only is this true, but the investigation 
of various drugs has determined the specific chemo-therapeutic treat- 
ment of infections. Examples of this are seen in the use of quinine 
in malaria, arsenic in trypanosomiasis and spirochetosis, and of 
emetin in amebiasis. The treatment based more particularly upon 
immunological methods has been largely specific, but more recent 
studies have given encouragement in the use of certain non-specific 
methods of treatment. It was found, for example, that the use of 
typhoid vaccine is of value not only in the treatment of typhoid 
fever, but in other diseases, and typhoid vaccines either in the form 
of the usual killed organisms or organisms sensitized with specific 
immune sera have produced beneficial results in such diseases as 
acute articular rheumatism, sub-acute and chronic arthritis, and in 
certain other infections. Similarly the use of blood serum, of pure 
proteins, of leucocyte extracts, of fibrin derivatives, and of certain 
other protein derivatives has appeared to be beneficial. It is not to 


be assumed that this method of non-specific treatment is of con- 
clusively proven value, but the effects observed in a certain per- 
centage of cases offers the hope that the method may be so perfected 
as to give improved results. 

The general reaction following subcutaneous injection of these 
substances may or may not be severe, but if they are administered 
by the intravenous route the reaction is likely to be pronounced. 
Frequently a chill appears and almost all cases develop fever which 
may be very high. Sometimes there is a general feeling of discom- 
fort associated with headache and nausea. In typhoid fever it is 
reported that hemorrhages not infrequently occur as the result of 
the therapeutic use of sensitized and of non-sensitized typhoid vac- 
cine. This does not appear in other diseases, and although pro- 
tein substances and their cleavage products, upon injection, tend to 
decrease the coagulation time, yet the use of blood serum in the treat- 
ment of hemophilia often has a favorable effect in preventing hemor- 
rhage. In addition to the possibility of hemorrhage in typhoid fever 
there are definite contraindications to this form of therapy in preg- 
nancy, in patients with organic heart disease, and in those with high 
blood-pressure. The influence of this non-specific method of treat- 
ment is not clearly understood. The question as to whether or not 
the known forms of antibodies are liberated or stimulated has been 
studied by numerous workers with contradictory results. Some 
have found an increase of agglutinins and precipitins for the specific 
organisms concerned in the disease, following non-specific protein 
injections, but this is contradicted by other workers. Regardless of 
the question of stimulation of special immune bodies it is important 
to know what other protective influences may be set at work. 

Fever is a common incident of the injection of proteins or pro- 
tein products, especially when they are given intravenously. This 
is sometimes accompanied by leucocytosis, but neither leucocytosis, 
marked acceleration of pulse-rate, nor the other clinical accompani- 
ments of fever necessarily appear. It has been demonstrated that 
increased temperature aids in the production of agglutinins and bac- 
teriolytic substances. In most instances the degree of temperature 
reached in fever has no deleterious effect directly upon the bacteria 
concerned, except possibly in the case of infections with the 
gonococcus and with the spirochete of relapsing fever. It has 
been suggested that high body temperature may favor the com- 
bination of the antigen and immune substances, but this has not 
been conclusively demonstrated. The injection of proteins may lead 
to an increase in the number of circulating leucocytes, although this 
is not invariably the case. The influence of such a hyper-leucocytosis 
in combating infection is at least partly because of the fact that 
these cells ingest and destroy bacteria. Nevertheless, certain 
infectious diseases, such as typhoid fever, may run their course 
without exhibiting leucocytosis, and it is therefore not essential for 
recovery that the leucocytes be increased in number. It must be 


pointed out, however, that phagocytosis is not the only way in 
which an increase of leucocytes may operate beneficially. The 
studies of Hiss and Zinsser indicate that extracts of leucocytes have 
a beneficial effect on infections and others have confirmed these 
results. Bail claims that a fresh emulsion of leucocytes will aid in 
neutralization by the specific anti-serum of endotoxin obtained from 
cholera vibrios. Jobling and Bull, however, demonstrated that leu- 
coprotease " will destroy the toxic extracts of typhoid bacilli and 
meningococci, and it is not improbable that a similar explanation 
will apply to the results obtained by Bail." 

There are other possible changes in the blood as the result of the 
injection of protein. The work of Jobling and his collaborators has 
thrown great light on the alterations of ferments and anti-ferments 
in the blood under a wide variety of conditions. The injection of 
various substances is almost invariably followed by a considerable 
mobilization of the serum ferments, more particularly the protease, 
and usually also the esterase. The value of the protease is probably 
in the direction of breaking down toxic split-protein products, which 
probably originate during the course of infectious disease, as the 
result of the splitting of bacteria and perhaps also of the body pro- 
teins. Protease does not act directly upon living bacteria, but it is 
to be considered possible that the esterase may break up the lipoid 
or lipoid-protein surface of the bacteria and therefore aid in their 
destruction. If we concede that the toxic protein split products aid 
in the virulence of bacteria it is possible that even although the 
protease simply breaks down these products into simpler non-toxic 
substances and does not directly attack the bacteria, yet the relief to 
the body afforded by this detoxifying action may assist it more 
permanently in combating disease. In certain states, such as preg- 
nancy, in disease such as cancer, and in the course of vaccine treat- 
ment the anti-ferment titer of the blood has been found to be high. 
Jobling and Peterson found that the anti-ferment power of the blood 
depends upon the amount of unsaturated lipoids present in highly 
dispersed phase in the serum and Bogolemez suggests that lipoids 
may serve to inhibit toxins, as is true in relation to the toxin of 
bacillus botulinus. Anti-ferment is not increased following protein 
injections and plays no part in the non-specific therapy of infectious 
disease, but inasmuch as the change may be seen in immune states, 
such as that following vaccination, it may be of importance in non- 
specific resistance to infection. In addition to the changes in fer- 
ments Jobling has found that the injection of non-specific proteins 
may produce changes in the viscosity of the serum. It is known 
that if precipitates are formed in serum by the action of a specific 
precipitating serum, conditions favorable to protease activity are 
produced and the changes in viscosity produced by protein injec- 
tions may similarly aid proteolytic activity. These changes in 
ferment content and physical character of the serum are of short dura- 
tion and are probably contemporaneous with the chill and fever. 


They do not directly account for permanent improvement seen in 
many patients, but if they rid the body of toxic substances for a 
short period of time the natural resistance may thereby become 
more effective than would otherwise be the case. 

The Site of Antibody Formation. Aside from a few fairly well- 
established facts the problem as to exactly where antibodies are 
formed still remains obscure. In general it is assumed that anti- 
bodies are not products of simple inversions of the foreign protein 
substances parentally introduced or as particular functions of spe- 
cial organs, but are the result of general cell reactions on the part 
of the host. Much evidence points to the lymphatic organs, the 
spleen, the liver, and the bone marrow as places where antibody 
formation is most active. Metchnikoff thought that antitoxins and 
bacteriolysins originate in the lymphatic organs and more particu- 
larly in the spleen and the bone marrow. Bordet attempted to 
show that bacteriolysins are derived from the leucocytes. Pfeiffer 
and Mark injected dead cholera spirilla into animals, exsanguinated 
these five days after the injection, and found the antibodies more 
concentrated in the spleen than in the blood serum itself. These 
authors also found that after a single injection of these organisms, 
the spleen, the bone marrow, and the lymph-nodes contained the 
specific antibodies before they could be detected in the blood, and 
further that as time passed these tissues became less active in spite 
of the fact that the bacteriolysins increased in the blood. Deutsch 
corroborated these findings with bacillus typhosus and Castellani 
with bacillus dysenterise. These authors agree, however, that the 
spleen is not essential, since its removal but slightly inhibits the 
formation of antibodies. Hektoen's experiments demonstrated that 
in dogs splenectomy just before and after the injection of alien 
blood-corpuscles was followed by a much lower, but otherwise typi- 
cal antibody curve, than is usually the case in dogs under normal 
conditions. London also reported a decreased formation of 
hemolysins after splenectomy, but this work has been contradicted 
by Yakuschewitch. Karsner, Amiral, and Bock found that splenec- 
tomy produces no change in hemopsonins of the circulating blood 
that is clearly demonstrable by in vitro test, and that the blood from 
the spleen is no richer in hemopsonins than is blood from other 
organs. Carrel and Ingebrigsten have produced hemolysins in the 
growing embryonic spleen. More recently Przygode succeeded in 
producing precipitins in vitro by culture of splenic tissue, and Miiller 
by transplanting splenic tissue from guinea-pigs, previously injected 
with sheep corpuscles, into the peritoneal cavity of normal guinea- 
pigs. It seems to us that since the spleen is an organ physiologically 
designated for the destruction of erythrocytes and also of other 
foreign substances through the activity of its hemophages, splenic 
tissue on transplantation will carry with it much antigenic sub- 
stance. Whether or not these hemophages participate in antibody 
production is at present difficult to say. 


For rapid production of antibodies Violle injected organisms 
directly into the gall-bladder. This fact is of interest because it 
indicates a possible function of the liver in the production of immune 
bodies. Miiller claims to have been able to stimulate the formation 
of hemolysin in liver tissue suspended in Ringer's solution outside 
the animal body. By perfusing the organ with solutions contain- 
ing iodine (iodipin) the effect was augmented, and he believes that 
in the normal animal the iodine of the thyroid may play a certain 
role in stimulating this special activity of the liver. Gay and Rusk 
found no evidence to uphold the supposed influence of iodipin. 
Hektoen and Carlson believe that both the spleen and liver are equally 
concerned in antibody formation, but Hektoen and Curtis found 
that in rats removal of about one-half of the liver appears to have 
no effect on the development of hemolysin for sheep corpuscles. 
The liver, just as the spleen, possesses highly active phagocytic 
endothelial cells which may play an important role in the produc- 
tion of antibodies. 

Numerous authors have shown that agglutinins appear in the 
blood stream before they are present in the extracts of any organ. 
The question, however, of whether or not the leucocytes are in- 
volved in this generative process is a matter of considerable contro- 
versy. Achard and Bensaud and others controvert the leucocytic or 
local origin of agglutinins, whereas Cantacuzene and also Swerew 
support this local origin in the formation of precipitins ; they noted 
a hypoleucocytosis followed by a marked hyperleucocytosis, which 
they think is responsible for the liberation of precipitins. Petit and 
Carlson, Vaughan, Cumming, and McGlumphy found that sub- 
stances like egg-white and serum disappear quickly from the cir- 
culating blood ; in fact, within a few hours after the introduction of 
these substances. Gay, however, has shown by means of comple- 
ment-fixation that even in immune animals such antigens are dem- 
onstrable after twenty-four hours, but not after forty-eight hours. 
It was not possible to demonstrate the antigen by the fixation method 
in organs like spleen, lymph-nodes, liver, kidney, and muscles, 
either at the time antigen was present in the blood or twenty-four 
hours thereafter. That the cells lining the blood-vessels may have 
certain powers of antibody production may be shown by the fact 
that a blood-vessel from an animal which has received several injec- 
tions of sheep erythrocytes and which has been dissected out soon 
after death of the animal and washed free from blood, has the power 
to hemolyze a suspension of fresh, non-sensitized sheep cells (Van 
Calcar). Kraus and Levaditi furthermore have shown that there 
exists a certain relationship between precipitins and the number of 
circulating leucocytes. Acute loss of blood profoundly affects anti- 
body production. The earliest observations seem to have been those 
of Roux and Vaillard. They found that in horses actively im- 
munized against tetanus toxin, bleeding causes a drop in the anti- 
toxin content in the blood, followed by a sharp rise in a short time. 


By continuous daily bleedings Hahn and Langer recently succeeded 
in increasing the agglutinin content 250,000 times its original value. 
Similarly Madsen and Tallquist have shown that certain poisons 
which destroy erythrocytes may increase the production of anti- 
bodies possibly by the action of the same mechanism as that whereby 
hemorrhage stimulates antibody formation. Rusk has found that 
animals intoxicated with benzol produce hemolysins and precipitins 
much less efficiently than normal animals. Since benzol affects 
particularly the bone marrow and the lymphatic apparatus, this 
evidence points in favor of the view that these tissues are largely 
involved in the production of hemolysins and of precipitins. 

According to Hektoen and Curtis, adrenalectomy in normal dogs 
and in dogs at the height of the antibody curve after the injection 
of rat corpuscles does not cause a decrease in the antibody content 
of the blood serum. Gates was able to remove approximately three- 
quarters to seven-eighths of the adrenal tissue of guinea-pigs with- 
out causing symptoms of adrenal insufficiency. Guinea-pigs thus 
treated were injected with bacillus typhosus and with hen cor- 
puscles, and the results demonstrated that adrenalectomy had no 
influence upon the rise or persistence of antibodies in the blood, 
and therefore the adrenals appear to play no essential part in the 
mechanism of antibody production. 

The results of Tjeldstad had shown that thyroidectomy failed to 
influence antibody production. Similar observations were recorded 
by Hektoen and Curtis, and others, but Frouin was more conserva- 
tive in his conclusions, and Garibaldi has recently renewed an in- 
terest in this matter by reporting that the hemolytic titer of the 
serum of thyroidectomized rabbits is much higher than that of his 
control animals, therefore concluding that thyroidectomy definitely 
favors antibody production. 

We know from the experiments of Wassermann and Takaki that 
brain substance neutralizes tetanus toxin, but this fact does not 
indicate this organ to be of much importance in the production of 
antibodies. In fact, we have learned from the experiments of Loewi 
and Meyer that injection of toxin into the nervous system produces an 
increased susceptibility of the animal rather than increase of resistance. 

Production of Antibodies at Site of Injection. Certain experi- 
ments indicate that antibodies may also be produced at the place of 
introduction of the antigen. Romer and also von Dungern have 
shown that immunization by way of the conjunctiva or anterior 
chamber of the eye results in the formation of antibodies in the 
aqueous humor before they can be demonstrated in the blood. These 
experiments also demonstrated that the opposite eye produces no 
antibody. Wassermann and Citron ligated a rabbit's ear at its base 
after a subcutaneous injection of bacteria. The ligation was left 
for several hours, and after nine days the bactericidal titer of the 
blood serum determined and the ear amputated. An immediate and 
rapid drop of antibody in the blood which occurred after the ampu- 


tation indicates that the main source of antibody formation was 
removed or the absorption of the antigenic substances entirely 
stopped. Forsmann and Lundstrom studied the curve of pro- 
duction of botulinus antitoxin following single intravenous or 
subcutaneous injection of the toxin. The curve following the 
subcutaneous injection reached its highest level on the fifteenth day, 
while that following the intravenous injection attained the maximum 
on the tenth day. It must be inferred that the subcutaneous method 
of injection introduces the factor of slow absorption, but it is also 
possible that some local factor may enter into the phenomenon. 
Immunization of horses with diphtheria toxin results in a greater 
yield of antitoxin when the horses are injected subcutaneously, but 
this does not necessarily prove a local production of antitoxin at the 
site of inoculation. Local cellular participation in immune reactions 
will be discussed further in the chapter on hypersusceptibility. 
There is little doubt that local reactions are of significance and that 
absorption may be influenced by local changes. The production of 
circulating antibodies in any considerable amounts undoubtedly re- 
quires more extensive cellular activity than that about the site of 
local inoculations. 



























General Nature of Toxins. Toxins are soluble poisonous prod- 
ucts of life processes, which on injection into animals lead to the 
formation of antitoxins. A corollary of this definition sometimes in- 
sisted upon is that the injurious effect of these toxic bodies must be 
preceded by an incubation period, but in certain instances this in- 
cubation time is a matter of minutes or hours, as is the case with 
certain snake poisons. The toxins are divided according to their 
origin into phytotoxins, produced by vegetable life, and zootoxins, 
produced by animal life. The most important of the phytotoxins 
are the bacterial toxins, but the group includes also ricin, abrin, 
crotin, robin, and curcin. Certain of the higher plant poisons which pro- 
duce the varieties of " hay fever " in susceptible individuals were 
formerly considered as toxins, but this view has now been discarded. 
The poison of rhus toxicodendron (poison ivy) and of rhus diversiloba 
(poison oak) might be considered a phytotoxin, but is chemically a glu- 
coside and does not produce antitoxin. The poisoning of non-edible 
mushrooms is due, in the case of amanita muscaris and helvella escul- 
enta, to definite chemical compounds, muscarine and helvellic acid, 
which do not produce antibodies. In the case of amanita phalloides 
there are two substances of toxic nature, a thermolabile hemolytic 
glucoside capable of producing an anti-hemolysin, and a thermo- 
stabile toxin of unknown composition and incapable of producing a 
definite immune body. The most important of the zootoxins are the 
snake venoms, but this group also includes the poisons of spiders, 
scorpions, centipedes, bees, wasps, hornets, dermal glands of toads 
and salamanders, various sera, notably that of the eel, and certain 
poisonous fish. 

Nicolle, Cesari, and Jouan divide the toxins into those that ap- 
pear in the form of definite secretions, as snake venoms, those which 
are determined by logical inference, as the toxins in microbial fil- 
trates, and those which are obtained by simple maceration, expres- 
sion, grinding, or autolysis, the endotoxins. Experiments with the 
end6toxins are performed in large part with the microbial bodies, 
and therefore these workers refer to the endotoxins as solid toxins. 

The bacterial toxins are synthetic products of the life of the organ- 
isms themselves. It was thought for years that the bacteria could 
synthesize the protein toxin from simple nitrogen-containing com- 
pounds. More modern studies oppose this view and state that more 
complex substances, such as proteoses and polypeptids, are essen- 
tial. It seems certain that nothing less complex than the amino- 
acids can be synthesized, and recent studies indicate that diphtheria 
toxin is not a synthetic product, but rather a catabolic substance 
elaborated by the bacteria only in the presence of amino-acids and 
certain additional substances, probably of the nature of vitamines. 
They are thus to be distinguished from the ptomains, which al- 
though products of bacterial growth, are in reality formed from the 
culture medium and vary according to the medium rather than 
according to the organism. The chemical nature of the bacterial 


toxins is uncertain, but they appear to be more closely related to the 
proteins than to any other known substance. They diffuse through 
membranes less slowly than do proteins, and therefore are pre- 
sumed to have a smaller molecular size. On the other hand, they 
are digested less readily than proteins. Like proteins they are 
electro-positive colloids, and are precipitated by protein precipitat- 
ing agents, such as ammonium sulphate. As against this is the 
statement that toxins may be so far purified that they do not give 
the protein reactions. They resemble enzymes in that both are 
colloids, both thermolabile, dialyze with difficulty, lose strength in 
passing through porcelain filters, resist drying and dry heat, resist 
low temperatures, both produce antibodies, both deteriorate after 
standing in solution with loss of zymophore group, but without loss 
of haptophore or combining groups. The difficulty of establishing 
the toxins as enzymes lies in the fact that neither toxin nor enzymes 
have been isolated in, the pure state. Furthermore, they do not act 
according to the same chemical laws, the enzyme operating re- 
peatedly to produce a large effect in the course of time and the toxin 
acting in almost direct proportion to its quantity. In summary we 
may quote Oppenheimer as saying of toxins that, " we must be 
contented to assume that they are large molecular complexes, probably 
related to the proteins, corresponding to them in certain properties, 
but standing even nearer to the equally mysterious enzymes with 
whose properties they show the most extended analogies, both in 
their reactions and in their activities." 

Toxins may be injured in a variety of ways. They may be de- 
stroyed, with certain exceptions, by moist heat at about 80 C, and 
resist dry heat to over 100 C. Light operates in a general way 
according to its intensity and penetrating power and the action is 
intensified by the presence of oxygen. Diffuse daylight operates 
slowly, but direct sunlight, X-ray, and ultra-violet rays more rapidly. 
They are destroyed by fluorescent substances. Oxygen and oxi- 
dizing substances injure and destroy toxins both in vivo and in vitro. 
Certain chemicals are injurious, as the salts of bivalent and trivalent 
metals, but not of monovalent metals. Certain toxins, particularly 
dysentery and diphtheria, may be rendered non-toxic by acids and 
restored to toxicity by alkali. They may be bound by fats and 
lipoids, as illustrated in part, at least, by the neutralization of 
tetanus toxin by brain substances. Enzymes, such as pepsin and 
pancreatic juice, as well as bile, destroy certain toxins, so that they 
produce no symptoms following ingestion, the striking exception 
being botulinus toxin. The action of digestive ferments upon toxins 
has recently been studied in detail by Loewi. He finds that diph- 
theria toxin is destroyed by pepsin and ptyalin, that tetanus toxin 
is destroyed by trypsin and ptyalin, but not by pepsin ; and that 
dysentery toxin is destroyed by the action of the duodenal mucosa 
of rabbits, but resists digestion with trypsin, ptyalin, pepsin, 
and papayotin. 


Classification of Bacterial Toxins. The bacterial toxins are 
classified as exotoxins and endotoxins, the former appearing in the 
culture medium as soluble substances and the latter appearing within 
the bacterial bodies. These intracellular toxins can be liberated by 
digestion, autolysis, freezing and fine grinding, and by expression 
with a Buchner press. They cause the symptoms of their special 
diseases, and in the natural course of the disease are probably liber- 
ated either by autolysis or by the action of the enzymes of the cells 
or fluids of the host. The tendency to-day, however, is to accept 
the view that the so-called endotoxins are not produced as such, but 
are produced from the bacteria during the process of hydrolytic 
cleavage of the bacterial proteins by ferments provided by the host. 
Certain bacteria, such as diphtheria and tetanus, produce only exo- 
toxins, whereas the typhoid group and certain other organisms were 
supposed formerly to produce only endotoxins. However, Bull has 
shown that certain strains of the gas bacillus of Welch produce an 
active exotoxin, and Ecker has shown that certain strains of bacillus 
paratyphosus B produce exotoxins, and this has been confirmed by 
Aronowitch. Kraus has shown a similar relationship in bacillus 
dysenteriae. Studies of Admont Clark and Felton indicate that the 
streptococcus hemolyticus produces a filterable toxic product 
answering all the requirements of a true toxin. The production of 
exotoxins is important for practical purposes because the endo- 
toxins do not lead to antitoxin formation with the same degree of 
facility as do exotoxins. Recent studies by Olitsky and Kligler have 
shown that the dysentery bacillus (Shiga) produces a thermolabile 
exotoxin and a thermostable endotoxin, the latter not being neutral- 
ized by anti-exotoxic serum. A potent antiserum for both toxins 
can be developed in the horse. The exotoxin appears to have spe- 
cial affinity for the nervous system of the rabbit and the endotoxin 
operates particularly upon the intestine. 

Organisms which produce exotoxins show a considerable variation of 
this property, but, on the whole, such toxins are more virulent and more 
highly antigenic than the exotoxins of those organisms which are essen- 
tially endotoxin producers. Being more highly antigenic the antitoxins 
produced by exotoxins are the more powerful, as is well known in the 
case of diphtheria and tetanus antitoxins. Nicolle, Cesari, and Jouan 
maintain, on the basis of certain work with the bacillus of Nocard, that 
exotoxins and endotoxins are identical in the case of a given organ- 
ism, but the more recent studies of Olitsky and Kligler quoted above 
would indicate that this is not true of dysentery bacillus (Shiga), 
and therefore not a general law. 

The exotoxins include diphtheria toxin, tetanus toxin, botulinus 
toxin, dysentery toxin, paratyphoid toxin, and bacillus aerogenes 
capsulatus (perfringens) toxin. Toxins are produced also by 
bacillus edematiens (Weinberg), vibrion septique, bacillus of symp- 
tomatic anthrax, bacillus pyocyaneus, streptococcus, and bacillus in- 
fluenzse. In addition it is claimed by Kolmer and his co-workers 


that they have demonstrated in pneumonic exudates a pneumococcus 
toxin. A number of other organisms produce lytic bodies for red 
blood-cells or hemotoxins, such as staphylolysin and megath- 
eriolysin, capable of inducing the formation of antilysins. A lytic 
body for leucocytes is also produced by staphylococcus aureus. 

The pathological effects of toxins are fundamentally seen in the 
production of cloudy swelling and even fatty degeneration of the 
parenchymatous viscera, heart, vascular muscle, liver, kidney, and 
secreting glands. Local inflammation at the site of injection, some- 
times leading to necrosis, is a frequent finding. Diphtheria toxin 
may show, in cases of paralysis, myelin sheath degeneration or in- 
flammation of nerves, and in guinea-pigs usually shows marked 
congestion or hemorrhage in the adrenals. Botulinus toxin leads to 
meningeal and even cerebral thrombosis and small hemorrhages. 
Both botulinus toxin and tetanus toxin have a marked affinity for 
the nervous system, but the effects are seen in the form of func- 
tional disturbance rather than morphologically demonstrable change, 
except for the vascular changes produced by botulinus toxin. 

Formation of Antitoxins. Antitoxins are produced by the re- 
peated parenteral injection of the toxin. Parenteral injection signi- 
fies introduction into the body by routes other than absorption 
through the alimentary canal. The selection of the species of 
animal to be used depends in part on its demonstrated ability to 
produce antitoxin and in part in commercial establishments on the 
possibility of obtaining large volumes of immune serum. It is often 
found desirable to select a species which has natural immunity to 
certain toxins and by inoculation raise that immunity to a higher 
degree. This may be accomplished with less difficulty than if a 
susceptible species were used. This is true of the use of the horse 
in producing gas bacillus antitoxin. The same principle is employed by 
Kyes in using fowl for the production of an anti-pneumococcus 
serum, although in this case it is not clear that the serum is an anti- 
toxic serum. Kyes states that the antiserum is antibacterial, i.e., 
agglutinating and bacteriolytic. Especially in the case of suscep- 
tible animals and also in relatively immune animals it may be neces- 
sary either to dilute the toxin to a very high degree or to attenuate 
it by other means, and thus consume considerable time in develop- 
ing a high degree of immunity. For immunizing guinea-pigs against 
diphtheria toxin Behring and Kitasato used iodine terchloride, 
and Roux and Martin, Lugol's solution. Frankel heated the 
toxin to 60 degrees. Behring in the case of tetanus toxin used 
a neutralized mixture of toxin and antitoxin, gradually reduc- 
ing the amount of antitoxin, and finally using unmodified toxin. In 
a sense this latter method has been employed by Behring and by 
Park for producing active immunity to diphtheria in children, al- 
though here it has been found unnecessary to use pure toxin with- 
out antitoxin to attain the desired result. It is believed that after 
injection there is a dissociation of the mixture, which permits the 


toxin to induce active antitoxin production by the patient's own 
body. In the work with animals the injections are given at inter- 
vals of a few days, sometimes interspersed with rest 'periods of 
about a week, until testing of small amounts of serum shows that a 
satisfactory result has been attained. 

Technic of Producing Diphtheria Toxin, and Antitoxin. Some details of 
the technic of producing diphtheria antitoxin may well serve as an example of the 
general phases of the method. It was early noted that different strains of the 
diphtheria bacillus produced toxins of variable strength and also that the same 
strain showed slight variation. Finally the strain isolated by Park and Williams, 
now well known as Park No. 8, a strong toxin producer, was selected as a standard 
and is so used throughout the world. In order to obtain the best aerobic conditions, 
a wide-bottom flask is employed so as to expose a large surface of the medium, 
" bob " veal broth being selected as most desirable. The culture is planted super- 
ficially and allowed to grow for seven or eight days. It is wise to use a culture that 
has been grown for several generations on the surface of broth tubes, the tubes 
so inclined as to expose a large broth surface. This accustoms the organisms to 
freely aerobic conditions. After the period of growth in the flask the organisms 
are killed by formaldehyde or by phenol, or even by heat, and the broth filtered 
either through paper or through a porcelain filter, preserved with toluol and per- 
mitted to "ripen," This ripening is made desirable because of progressive deteriora- 
tion of the toxin, a phenomenon which will be more profitably taken up in the 
discussion of the toxin-antitoxin combination. 

The following table shows a scheme as actually practised for producing 
diphtheria antitoxin. All the injections are subcutaneous. 

July 22 6,000 units antitoxin 

25 400 minimum lethal doses of toxin (see page 45) 
27 800 minimum lethal doses of toxin 

29 1. 200 minimum lethal doses of toxin 

Aug. i i, 600 minimum lethal doses of toxin 

3 2,000 minimum lethal doses of toxin 

5 2,500 minimum lethal doses of toxin 

8 3,000 minimum lethal doses of toxin 

10 3,600 minimum lethal doses of toxin 

12 4,400 minimum lethal doses of toxin 

15 5,200 minimum lethal doses of toxin 

17 6,200 minimum lethal doses of toxin 

19 7,200 minimum lethal doses of toxin 

22 8,500 minimum lethal doses of toxin 

24 10,000 minimum lethal doses of toxin 

26 13,000 minimum lethal doses of toxin 
29 16,000 minimum lethal doses of toxin 
31 20,000 minimum lethal doses of toxin 

Sept. 2 24,000 

5 28,000 
7 32,000 
9 36,000 

Lengthen intervals by 24 hours if made 
necessary by severe reaction. 

12 40,000 

Trial bleeding separation of and testing of serum, September 21. After that 
if further immunization is necessary the dose is raised 5000 M.L.D. each injection. 

The Nature of Antitoxins. The serum thus obtained contains 
the antitoxin. The exact nature of the antitoxin is unknown, but 
chemical examination and other studies have thrown a certain 
amount of light upon its properties. If we can accept the division 
of the serum protein into fibrinogen, euglobulin and pseudo-globulin 
by precipitation with magnesium sulphate or ammonium sulphate, 
the antitoxin is found in that water-soluble fraction known as 



pseudo-globulin, which constitutes about 78 per cent, of the serum 

protein. This fact is taken advantage of in the so-called concentra- 

tion of antitoxin, in which the pseudo-globulin is thrown down by 

the addition of ammonium sulphate. Heinemann states that pseudo- 

globulins may be broken into fractions, one of which contains the 

antitoxin in highly concentrated 

form, thus making the bulk even 

smaller than by the use of pseudo- 

globulin. The precipitate is col- 

lected, dialyzed free of salt, and 

taken up in water, the final volume 

being considerably less than the 

original amount of serum, there- 

fore containing a greater number 

of antitoxic units per c.c. than the 

whole serum. This does not mean 

that the antitoxin is necessarily a 

globulin, for it resists trypsin diges- 

tion in greater degree than does 

globulin. It is, however, an elec- 

tro-positive colloid. Antitoxin is 

not thrown down in indifferent 

precipitates, and in this respect dif- 

fers from the enzymes, nor does it 

operate in the same quantitative re- 

lations as enzymes. The large size 

of the antitoxin molecule is indi- 

cated by the famous Martin and 

Cherry experiment, which showed 

that if toxin and antitoxin are 

mixed and passed through gelatin 

filters the toxin appears first. The FIG. I. Apparatus for filtration through porce- 

nninr wa<5 hrniifrVit nut hv lam f sm ^ u quantities of material. Between the 

Was fOUgnt OUt Dy rubber tube and the suction apparatus must be 

t-i/-l TVT o A c. e* n -wrVir> inserted a small trap to prevent entrance into the 

nd MadS en, wno fl ask of water when suction is released. The trap 

showed that toxin diffuses ten times is a 8alt ^ utlet tube 

more rapidly than antitoxin. Anti- 

toxin is injured by moist heat of 60 to 70 C, destroyed by moist heat 

of 100 C., and by dry heat of 140 C. 

The influence of temperature on antitoxin is of the utmost prac- 
tical importance in regard to its preservation for therapeusis. 
Anderson has estimated the yearly deterioration at different tem- 
peratures as follows : 

26-35 C. 

15 C. 


Yearly deterioration 
20 per cent. 
10 per cent. 
6 per cent. 


McConkey has given the following rates of deterioration : 

Temperature Deterioration in 6 months 

36 C. 37 per cent. 

6-i6 C. 14 per cent. 

Ice chest 7 per cent. 

The second figures in McConkey's table indicate room temper- 
ature in winter and summer. Although the two series of investi- 
gations differ in actual figures, they serve to show that the only 
temperatures for satisfactory preservation are those of the ice chest. 
Antitoxin is destroyed by putrefaction of the serum, by acids and 
alkalies, by ultra-violet rays and deteriorates in solution, by expo- 
sure to light and air. Ingestion into the alimentary tract destroys 
antitoxin. Nevertheless, it is stated that suckling infants can absorb 
antitoxin from the mother's milk. Toxin disappears from the blood 
in the neighborhood of from seven to .eleven days after injection, it 
being in part destroyed, in part bound by the tissues, and in very 
small part excreted in the urine. Antitoxin appears in man very 
early in life, as determined by the Schick test (see page 53). It has 
not been proven why the antitoxin develops, that is, whether it is 
natural or the result of slight attacks of the disease. As indicated 
above, it may possibly be transferred in mother's milk. Sherman 
states that lysins and complement are inappreciable in the youngest 
swine embryos, but that after the ninth week of gestation they can 
be demonstrated in varying amount. Whether they are autoch- 
thonous or transmitted from the mother has not been determined. 
Wells states that, " taken together, the evidence indicates a closer 
resemblance of antitoxins to proteins than has been shown for the 
toxins, and all attempts to separate antitoxins from proteins have 
so far failed." 

The manner in which antitoxin neutralizes toxin is the subject 
of much discussion, experiment, and hypothesis. Before discussing 
the matter from a theoretical point of view, it is advisable to explain 
some of the technical operations in the standardization or titration of 
the antitoxin. From the practical point of view this is now rela- 
tively simple, although requiring an extremely precise method, but 
the earlier investigators were beset with many difficulties. 

Standardization of Diphtheria Antitoxin. In diseases such as 
diphtheria and tetanus, where the symptoms are the results of the 
action of the toxin, it is necessary to determine the amount of anti- 
toxin required to protect an animal against the effect of a given 
amount of toxin. The earlier investigators attempted to determine 
the amount of antitoxic serum necessary to protect against inocula- 
tions with living organisms, but the variability in biological proper- 
ties of growth and toxin production, infection, and resistance, soon 
showed the unreliability of this method. Behring then took up the 
determination of antitoxin against toxin, but found it difficult to 
standardize such a method over a wide geographic area because of 


differences in bacterial strains and variations in the same strains 
growing under even slightly different conditions. Ehrlich sought to 
reduce the factor of error by determining the antitoxic " unit " as 
the amount of antitoxic serum necessary to protect against ten times 
the minimum lethal dose. Even this was unsatisfactory, and Behring 
and Ehrlich in collaboration settled upon an arbitrary method of 
determining a " normal " toxin and a " normal " therapeutic serum. 
The "normal" toxin contained in i.o c.c. one hundred times the 
minimum lethal dose for a guinea-pig of 250 grams. The " normal " 
therapeutic serum was tested and diluted so that o.i c.c. contained 
sufficient antitoxin to neutralize i.o c.c. of the "normal" toxin or, 
in other words, i.o c.c. antitoxic serum, as a unit, was capable of 
neutralizing 100 minimum lethal doses of toxin. The fundamental 
error, however, had not been overcome by this method, and it was 
found that no method which had as its basis a toxin, could be ap- 
plied over a large area and the method was finally abandoned. 
The toxin deteriorates rapidly on standing, and even though 
after a time it becomes fairly stable, it still is insufficiently so 
to justify its use for purposes of standardization. On the other 
hand, the antitoxic serum resists drying for an indefinite period, and 
if used as a standard can be shipped great distances. The standard 
in this country has been established by the United States Public 
Health Service. The unit of antitoxin as now used has no direct 
relation to the unit of " normal " therapeutic serum as defined by 
Behring and Ehrlich, but by interchange between nations it is 
practically constant throughout the world. Hence, if a laboratory 
wishes to prepare an antitoxin the standard unit of antitoxin can be 
obtained from the Public Health Service. With the standard anti- 
toxin on hand, the antitoxic content of a newly prepared antiserum 
may be determined. This must be done through the medium of a 
toxin whose strength is titrated against the standard antitoxin ; the 
toxin is thereby standardized, so that the strength of the new anti- 
toxic serum can be measured. The toxin must be one which has 
been ripened, so that any deterioration during the few days' time 
necessary for titration against the standard immune serum and then 
against the new serum, is reduced to a negligible minimum! In 
order to make the titration against the standard antitoxic unit some- 
what easier it is well to know the minimum lethal dose of toxin. 
There are then to be determined : 

1. The minimum lethal dose of toxin (M.L.D.). 

2. The L dose of antitoxin. 

3. The L + dose of antitoxin. 

The minimum lethal dose of toxin is determined by injecting subcuta- 
neously, varying doses of toxin into a series of guinea-pigs 250 grams in 
weight. Healthy pigs of this weight are usually young and less expensive 
than fully-grown animals. The M.L.D. is the smallest dose that kills a 
pig in from four to five days. Less than four days means too great strength, 


more than five days too little strength. It can be seen that the selection of 
the weight of the pigs and the length of time are arbitrary but universal 
standards. A strong toxin might give results as follows: 

Guinea-pig Toxin dose Result 

1 0.0036 c.c. Lives 

2 0.0038 c.c. Dead 6 days 

3 0.0040 c.c. Dead 4 days 8 hours 

4 0.0042 c.c. Dead 3 days 20 hours 

5 0.0044 c.c. Dead 2 days 

Guinea-pig No. 3 died at the right time interval and 0.004 is the M.L.D. 
of this toxin. Experiments with a preliminary series using more widely vary- 
ing doses of toxin would be necessary before the final experiment could 
be set up. 

The Lo dose {Limes null) is that amount of toxin which is so thoroughly satu- 
rated with one unit of antitoxin that neither local nor general symptoms 
appear following the injection of the mixture. An experiment follows: 

Guinea-pig antitoxin Toxin . Result 

1 i unit 0.36 c.c. No reaction 

2 i unit 0.38 c.c. No reaction 

3 i unit 0.40 c.c. Barely visible congestion 

4 i unit 0.42 c.c. Moderate inflammation 

5 i unit 0.44 c.c. Distinct inflammation 

In this experiment the dose of toxin, 0.40 c.c., given pig No. 3, is the L 
dose. The note as to reaction refers to the shaven site of injection. 

The L dose {Limes death) indicates the smallest amount of toxin which 
after mixture with one unit of antitoxin will produce death in four-five days. 
The plus sign is the mark used in English texts to correspond to the cross 
mark used in German literature to signify death. An experiment follows : 

Guinea-pig antitoxin Toxin Result 

unit 0.44 c.c. Lives 

unit 0.46 c.c. Dead 6 days 

unit 0.48 c.c. Dead 4 days 

unit 0.50 c.c. Dead 3 days 

unit 0.52 c.c. Dead 2 days 

In this experiment 048 c.c. given guinea-pig No. 3 is the L + dose of toxin. 

Titration of Diphtheria Antitoxin. In the actual titration of an 
antitoxin as practised to-day there must be at hand a standard anti- 
toxin of known strength as well as a toxin, whose M.L.D. has been 
at least approximately determined. The antitoxin has been dried 
in a vacuum and preserved in sealed U-shaped ampoules which con- 
tain the antitoxin in one arm and P 2 O 5 or some other hygroscopic 
substance in the other arm, in order to maintain the dryness of the 
antitoxin. The ampoule is best kept in a light-proof box in the re- 
frigerator. Against this antitoxin the L + dose of a toxin is deter- 
mined, and against this toxin the new antitoxin is titrated. The 
amount of antitoxin which protects against the L + dose for four 
days is the antitoxin unit of the new serum. In preliminary experi- 
ments the antitoxin is roughly titrated in dilutions of i : 100, 1 : 200, 
1:300, and so on. In each case the antitoxin is used in i.o c.c. 
amounts and the toxin so diluted that 2.0 c.c. contain the M.L.D., 
the two being mixed and allowed to stand at room temperature for 



one hour. The Rosenau glass syringe for this purpose has an 
oblique side arm for salt solution, so that after the toxin-antitoxin 
mixture is injected, the side arm is swung around, emptying the 
saline into the main body of the syringe. The salt solution is then 
injected, thus washing out the remnants of the toxin-antitoxin mix- 
ture that may remain in the lower part of the syringe and needle. 

The following experiment will serve to illustrate, granting that the pre- 
liminary titration showed a strength of antitoxin between 1-200 and 1-400. 



i c.c. of each 



2.O C.C 

= M.L.D. 
2.O C.C. 
2.O C.C. 
2.O C.C. 
2.O C.C. 
2.O C.C. 
2.O C.C. 
2.O C.C. 
2.O C.C. 
2.O C.C. 
2.O C.C. 



5 days 
5 days 
4 days 
4 days 
3 days 
3 days 
3 days 
3 days 
2 days 
2 days 

1 I-20O 

2 -22O 

3 -240 

4 -260 

5 -280 

6 -300 

7 -320 

8 -340 

9 1-360 
10 1-380 

Thus doses i and 2 were more than sufficient to protect four days, and 
doses 5-10 were insufficient. Doses 3 and 4 protected for four days, and in 
order to be safe dose No. 3 of 1-240 would be selected. If the antitoxic unit is 
1/240 of i.o c.c., each c.c. of serum contains 240 units of antitoxin. In com- 
mercial work, the practice is to be absolutely on the safe side, and the next 
larger dose of antitoxin would be employed as the unit, and the serum 
marketed as containing 220 units per c.c. 

In the therapeutic use of such a serum the unit 
content of the serum is simply a guide to its use, 
the dose employed being rather on an empirical 
basis than otherwise, because of the uncertainty of 
the amount of toxin present in the body of the 
patient. It is generally assumed that the larger 
the extent of the exudate, the greater the amount 
of toxin produced and the larger the absorbing sur- 
face, but it can readily be seen from the theoretical 
standpoint that variations may be produced by dif- 
ferences in toxin production by the different strains 
of bacillus diphtherise which may be encountered 
in patients. It is unwise to stress this latter possi- 
bility and preferable to regulate the dosage on the 
former basis. More will be said later regarding 

The Toxin-antitoxin Union. T he E hrlich 
Theory. With the foregoing practical considera- 
tion of antitoxin titration in mind, the theoretical 
problems of the nature of the toxin-antitoxin com- FlG ~ 2 .-~rT he 

r or Reichel syringe for 

bination will be taken up. The simplest conception injecting t9xin-anti- 

. . toxin mixture. 

is that antitoxin neutralizes toxin in the same way 

that a strong acid neutralizes a strong base. As has been seen, 

the neutralization is quantitative and follows in a general way 


the law of multiple proportions. If this were true, how- 
ever, the L + dose which in combination with the antitoxin unit 
kills a pig in four days should contain one unit more of toxin 
(i M.L.D.) than the L dose which just fails to produce symptoms. 
Reference to the experiments offered to illustrate the determination 
of M.L.D. , L dose, and L + dose show that the M.L.D. of the toxin 
was 0.004 c - c -> the L dose of toxin was 0.40 c.c. or one hundred times 
the M.L.D., and the L,. dose 0.48 c.c. or one hundred and twenty 
times the M.L.D. The difference between L and L + doses is, there- 
fore, twenty times the M.L.D. instead of exactly equal to it. This 
has been interpreted to indicate that some body or bodies, other than 
the toxin, has combined with the antitoxin, thus limiting its ability 
to combine with toxin. Ehrlich, after numerous experiments and 
hypotheses, reached the assumption that the toxic broth contains 
two bodies other than toxin, which he named toxon and toxoid. The 
toxon is a body with a smaller degree of affinity for the antitoxin 
than has the toxin. In a determination of the L dose the antitoxin 
neutralizes both toxin and toxon, so that no symptoms appear, but 
if more toxin be added to the mixture it combines with antitoxin, 
displacing the more loosely combined toxon. Finally, after suffi- 
cient addition of toxin the antitoxin is fully saturated, and any addi- 
tional toxin will be free, and if in sufficient quantity (i M.L.D.) 
will lead to the death of the experimental animal. In more detail 
the 20 M.L.D.'s necessary to make the difference between the L and 
L + doses were so used that 19 M.L.D.'s were employed to displace a 
proportionate amount of toxon and toxoid from combination with 
the antitoxin unit, and the remaining i M.L.D. sufficed to kill the 
pig in four days. If more than i M.L.D. were present in excess 
death would ensue after a shorter period, and if less than i M.L.D. 
were present death would occur later than four days or not at all. 
It is believed, on the basis both of experimental and clinical obser- 
vation, that toxon is responsible for the late paralyses of diphtheria. 
The conception of the toxoid is based on the Ehrlich assumption 
that the toxin molecule has a toxic fraction or " toxophore group " 
and a combining fraction or " haptophore group." A toxin will 
retain its binding power for antitoxin for a considerable length of 
time with little change in the L + dose, but with marked deterioration 
of toxic power and corresponding reduction of the M.L.D. This is 
interpreted as meaning that the toxic fraction is labile and the com- 
bining fraction much more stable. The toxoid, then, is the toxin 
molecule so altered that its toxic part is reduced and the combining 
part practically intact. As can readily be seen, this can account 
also in part for the discrepancy between L and L + dose. The 
discrepancy between L and L + dose in fresh toxic broth is be- 
lieved to be due to the presence of toxon rather than toxoid, be- 
cause too short a time has elapsed to account for toxoid formation. 
As the toxic broth becomes older the discrepancy becomes greater, 
even after a relative equilibrium has been established, and the differ- 


ence is believed to be due to the progressive formation of toxoid 
from toxin and perhaps also from toxon. Ehrlich and also Madsen 
found that the combination of one antitoxic unit with toxin in the 
determination of the L dose was in multiples of 100 M.L.D.'s. 
These multiples were rarely less than 100 and never more than 200. 
This would indicate that the multiple is not less than 100, but even 
though values of 200 are not obtainable, the failure may be ex- 
plained by the fact that pure toxin is not procurable. By means of 
the phenomenon of " partial absorption " Ehrlich established a 
formula for the antitoxin-toxin combination which he expressed as 
"toxin 200 antitoxin." This has been illustrated by means of a toxin- 
antitoxin " spectrum " based on a total valency of 200, the total valency 
including toxin, protoxoid, and toxon. In spite of the great academic 
interest of this discussion, its immediate practical value is not apparent 
and the reader is referred to larger works for complete discussion. 

Objections to the Ehrlich Theory. As indicated previously, the 
Ehrlich hypothesis is based on the assumption that the toxin-anti- 
toxin reaction follows in a fairly close manner the chemical reaction 
between a strong acid and a strong base. Certain features of the 
process of combination support the idea of chemical union, as, for 
example, the fact that warmth accelerates the reaction, dilution 
slows it. Furthermore, there is a liberation of heat in the reac- 
tion, that is to say, about half as much heat per gram molecule as 
would be liberated by the reaction between a strong acid and a 
strong base. It is well known, however, that the union of toxin and 
antitoxin is loose and within certain limits reversible. The Martin 
and Cherry experiment referred to earlier in this chapter is of great 
importance in this connection. They mixed snake venom and anti- 
toxin to a point of neutralization and filtered through gelatin filters, 
with the result that the toxin came through the filter first. This 
they interpreted as being due to the smaller size of the toxin mole- 
cule. It also shows the looseness of combination and the reversi- 
bility of the reaction. They further showed that the longer the 
mixture stands, the smaller the amount of toxin that comes 
through the filter. Zinsser states that the " chief value of these 
experiments lies in their proof of the element of time as an 
important factor in the toxin-antitoxin union." Calmette had previ- 
ously shown that venoms of certain snakes would remain virulent 
after heating even to 100 degrees, and that the antitoxins were 
thermolabile. He demonstrated that if the two were mixed so as to 
be non-toxic, subsequent heating would liberate the toxin probably 
through thermic destruction of the antitoxin. If the union were a 
fixed one, this should not have been true. Martin and Cherry failed 
to confirm this with the venom of an Australian snake, but this can- 
not be regarded as a refutation of Calmette's work, especially as the 
principle was found to apply to other toxins and antitoxins. 
Morgenroth showed that acidulation with HC1 of a venom lysin- 
antilysin mixture produced an acid-toxin molecule that resisted 


heat and could by heat be dissociated from the thermolabile anti- 
lysin. The subsequent chemical neutralization of the toxin (or 
lysin) resulted in the restoration of its toxicity. In this laboratory 
Wahl has shown that titration of diphtheria toxin using normal 
guinea-pigs in one series and guinea-pigs with only one kidney in 
another, gives materially different results. These experiments were 
carefully controlled and may be offered as a further indication of the 
loose combination and its corollary the reversibility of the reaction, 
on the probable assumption that the toxin is more readily excreted 
by the animals with two kidneys than by those with one. The 
recitation of these few experiments to which others might be added 
is sufficient to illustrate the objection to the Ehrlich theory of fixed 
combination, and two other important hypotheses are offered for 
consideration : (i) The conception that the combination follows the 
law of mass action and (2) the theory of colloidal reaction. 

The Law of Mass Action. The application of the law of mass 
action has been worked on by Arrhenius and Madsen principally. 
This law is usually illustrated in the chemical laboratories by the 
reaction between one gram molecule ethyl alcohol and one gram 
molecule acetic acid which yields ethyl acetate and water, the reac- 
tion, however, stopping at a point of equilibrium where there is 
found in the mixture y$ gram molecule alcohol, l /$ gram molecule 
acetic acid, 2 /$ gram molecule ethyl acetate, and 2 /$ gram molecule 
water. The same end-result is obtained if instead of mixing ethyl 
alcohol and acetic acid, we mix ethyl acetate and water, thus indicat- 
ing the reversibility of the reaction as stated in the formula : 


Arrhenius and Madsen compared the reaction between tetanoly- 
sin and its antitoxin and the reaction between boric acid and am- 
monia. This was of advantage because ammonia is hemolytic and 
boric acid is not. Thus a reversible reaction is found in which the 
addition of boric acid reduces the hemolytic activity of the ammonia. 
As with the alcohol-acetic acid experiment, however, a point of 
equilibrium is established whereby there always remains a small 
amount of free ammonia in spite of the addition of boric acid to a 
point of saturation. The same general proposition holds in regard 
to tetanolysin and antilysin, and these authors were able to con- 
struct similar curves of neutralization for both of these reactions. 
With this idea as a basis, the late paralyses of diphtheria, either ex- 
perimental or clinical, would depend not upon the toxon of Ehrlich, 
but rather upon a small non-fatal amount of toxin that is never com- 
pletely neutralized in the reaction. 

The Danysz Effect. It will readily be seen, however, that the 
reversible reactions illustrating the law of mass action deal with 
crystalloids, while it is probable both toxins and antitoxins are of 
colloidal character. Certain colloids are known as " reversible col- 


loids," but as yet there is little definite proof that reversible reac- 
tions between two colloids take place. According to certain inter- 
pretations, the most important observation in support of the 
colloidal theory is the Danysz effect. If the toxin is added to the 
antitoxin in fractions with an interval of time elapsing between, less 
toxin is needed to saturate the antitoxin than if the toxin were added 
in one volume. In other words, if i.o c.c. toxin were saturated 
in the usual way with o.i c.c. antitoxin and if in another test-tube 
the toxin is added to the same amount of antitoxin, not in a single 
dose, but in successive doses of 0.2 c.c., until i.o c.c. is present, this 
latter mixture instead of being neutral would be toxic. Wells, how- 
ever, states that this " indicates that the toxin antitoxin union is 
physical rather than chemical, for it seems to be quite analogous to 
such a phenomenon as the taking up of more dye by several pieces 
of blotting paper added in series to a dye solution, than by the same 
amount of paper added in one piece." Of somewhat similar import 
is the absorption theory of Bordet and of Landsteiner, which states 
that when toxin is added to antitoxin in smaller quantities than 
saturation, let us say five molecules of antitoxin to ten of toxin, this 
does not result in complete molecular combination with five mole- 
cules of toxin, but rather in half saturation of the entire ten mole- 
cules of toxin. This results in attenuation of the toxin, so that 
instead of there being five free molecules of toxin there are ten units of 
partly detoxified toxin. It is not to be expected that this follows in exact 
arithmetical progression, but Biltz has made comparisons with absorp- 
tion phenomena in general and finds fairly consistent results. 

In summary it may be said that in explaining the union of toxin and 
antitoxin the Ehrlich hypothesis does not withstand critical examination 
and that the reaction is in all likelihood of an intricate physico-chemical 
nature referable, in part at least, to the probable colloidal nature of the 
reacting bodies, but not as yet satisfactorily explained. 

Therapeutic Use of Diphtheria Antitoxin. In 1892 von Behring 
and Wernicke found that the serum of animals immunized against 
diphtheria toxin protects other animals of the same and different 
species against the action of the toxin. In 1894 Roux demonstrated 
the value of the treatment of diphtheria in man by means of anti- 
toxic serum. This method of treatment rapidly attained widespread 
use and has markedly reduced the mortality from the disease. 
Numerous statistical studies have been made since that time, and 
it is safe to say that the introduction of antitoxin treatment has 
reduced mortality from approximately 40 per cent, to approximately 
7 per cent. In interpreting the figures it has been found necessary 
to take account of two important factors ; namely, the cases of 
laryngeal diphtheria and the time at which treatment is instituted. 
Laryngeal diphtheria presents not only the element of toxic absorp- 
tion, but in addition mechanical obstruction to respiration and 
the possibility of extension downward, so as to produce pneumonia. 
Furthermore, the operative procedures for relieving the respiratory 


obstruction are such as to introduce an additional minor element of 
danger. The accidents following tracheotomy are distinctly more 
numerous than those following intubation, but neither operation can 
be regarded as absolutely without risk. It is now well established 
that the earlier in the course of disease the antitoxin is administered 
the more favorable is the prognosis. In order to present this 
graphically, however, we insert the following table taken in large 
part from Dieudonne and Weichardt : 

of cases 

ity per- 





















~ 7 












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The therapeutic efficiency of the antitoxin also varies accord- 
ing to the method of administration. According to Berghaus, 
intravenous injections are five hundred times more effective and 
intraperitoneal are eighty to ninety times more effective than sub- 
cutaneous injections. In the earlier days of antitoxin treatment the 
method was almost entirely subcutaneous injection, but subse- 
quently the intravenous method was employed in severely toxic 
cases. Injections were given at various intervals, usually a day 
apart, until the disease showed marked improvement. The studies 
of Park and his collaborators have modified the treatment consid- 
erably. Park was able to show that a single dose of antitoxin in 
sufficient quantity is more effective in neutralizing the circulating 
toxin than the multiple small doses, largely because of the fact that 
with subcutaneous and intramuscular injections the absorption is 
continuous, whereas during the period usually occupied by giving 
several doses, the absorption occurs for only a short time after each 
injection. Were it possible to determine for clinical purposes the exact 
amount of toxin absorption during the disease the dosage of antitoxin 
could be accurately regulated. Unfortunately, however, different strains 
of the bacilli vary in capacity for production of toxin and the depth 
and extent of the local lesion, as well as the nature of the underlying 
tissues, have some influence upon the rate and amount of absorption. 


Therefore, the actual dose employed is to a large extent upon an empiri- 
cal basis. Park recommends the following table of doses and methods 
of administration : 


Infant, ten to thirty pounds (under two years of age). 

Mild Moderate Severe Malignant 
2,000 3,OOO 5.OOO 

3,000 5,000 10,000 10,000 

Child, thirty to ninety pounds (under fifteen years of age). 
3,000 4,000 10,000 10,000 

4,000 10,000 15,000 20,000 

Adults, ninety pounds and over. 

3,000 5,ooo 10,000 15,000 

5,000 10,000 20,000 40,000 


Mild Moderate Severe Malignant 

Subcutaneous or Intramuscular or Intramuscular or y 2 intravenous and 
intramuscular subcutaneous y 2 intravenous y 2 intramuscular 

and y 2 intramus- or subcutaneous 
cular or subcu- 

McCombie recommends the following dosages : 
Mild: 4000 to 8000 units in one dose. 

Moderate: 12,000 to 16,000 units in one dose or two doses. 
Severe : 20,000 to 50,000 units or more in two or three doses. 
Laryngeal: 16,000 to 24,000 as initial dose, and repeat once or twice according 
to persistence of symptoms. 

Improvement following the administration of antitoxin is strik- 
ing when given early and exhibits itself in fall of temperature, reduc- 
tion of leucocytosis, reduction of inflammation, and separation of 
the fibrinous membrane. This improvement varies somewhat with 
the method of administration, the intravenous method effecting im- 
provement in somewhat less time than the intramuscular, and the 
latter in somewhat less time than the subcutaneous. In a series of 
cases studied in the City Hospital in Cleveland by Ruh the intra- 
venous form of administration was followed in 83 per cent, of the 
cases by a severe general reaction with chills and prostration com- 
ing on a few minutes after the administration and lasting for about 
twenty minutes. At the present time it is impossible to state the 
exact cause of this reaction. Such reaction does not follow subcu- 
taneous and intramuscular injections. It is not due to the preserva- 
tive, nor as far as can be determined, to the age of the serum. The 
most reasonable explanation appears to us to be that the reaction is 
due to foreignness of the horse protein. None of Ruh's cases showed 
prolonged or fatal reactions, and it is not probable that these reac- 
tions represent individual hypersusceptibility, because if this were 
true fatalities would be likely to occur (see page 230). 

Natural Immunity to Diphtheria The Schick Test. It has long 
been known that many individuals, even as many as 80 per cent, of 
adults and 50 per cent, of children, are immune to diphtheria, as indi- 


cated by demonstrating antitoxin in the blood. The methods of 
demonstration were not easily applicable until the development 
of the Schick test. This test is performed by injecting intra- 
cutaneously one-fiftieth of the minimum lethal dose of a specially 
prepared toxin contained in 0.2 c.c. of salt solution. Injection is pref- 
erably on the flexor surface of the arm or forearm. Six-day broth 
cultures of the organism are killed with phenol, sedimented in the 
ice-box for two or three days, the supernatant fluid filtered through 
a Berkefeld candle, and the clear filtrate accurately standardized. It 
is well to keep this filtrate for several months or a year, so that its 
rate of deterioration is reduced to a minimum. A control injection 
is given with the same quantity of toxic broth heated to 75 C, so 
as to destroy the toxin. 

The reactions to injections may be as follows: 

A. Positive reaction. This indicates that no antitoxin is present in the 
body, thereby permitting the toxin to act" upon the unprotected cells. Slight 
reaction appears in from twelve to twenty-four hours in the form of redness, 
which becomes more distinct in from twenty-four to forty-eight hours, reach- 
ing its maximum on the third or fourth day, then gradually disappearing and 
leaving an area of scaling and brown pigmentation. The area attains a 
diameter of 10 to 20 mm., and varies in intensity, depending on the sensitive- 
ness of the individual. 

B. Negative reaction. If no distinct reaction appears any more than is 
seen in the control area the failure to react indicates that an amount of anti- 
toxin is present in the body sufficient to neutralize the introduced toxin. Such 
a reaction in a child of about three years of age probably indicates perma- 
nent immunity. By varying the quantity of toxin injected, the amount of 
antitoxin can be titrated. 

C. The pseudo-reaction. This is usually urticaria! in nature, appearing some- 
times immediately and sometimes in from six to eighteen hours, reaching its 
maximum on the third or fourth day. It fails to leave pigmentation after it 
subsides. This is a reaction of hypersusceptibility to the protein substances 
present in the toxic broth as the result of the autolysis of the diphtheria 
bacilli, and is in nature the same as other reactions of hypersusceptibility 
described subsequently (see page 236). Such a pseudo-reaction may intensify 
the true reaction and represent a summation of the protein reaction and a 
reaction to the toxin. This must be taken to indicate that an individual may 
be hypersensitive to the proteins of diphtheria bacilli but at the same time 
not possessing in his circulating blood any antitoxin. The differentiation 
depends upon the difference between the reaction at the site of the test 
injection and at the site of the control injection. 

Zingher divides the positive reactions as follows : -f- -f- indicates a strong 
positive reaction with marked local redness, infiltration, and occasionally super- 
ficial vesiculatkm ; -f- indicates positive reaction with redness but little or no 
infiltration ; indicates moderately positive reaction with moderate degree of 
redness and no local infiltration ; indicates a faintly positive reaction with only 
slight redness and no local infiltration. 

The test has been found to be of great value in determining the 
immunity of groups of individuals, particularly in institutions 
where there has been exposure to diphtheria. It has also given con- 
siderable information as to the incidence and duration of this variety 
of active immunity. Immunity to diphtheria may be derived from 
the mother and lasts for about six months after birth. The largest 
number of positives is found from the ages of six to eighteen months. 
This gradually decreases throughout life. 

Another method for determining the presence of antitoxin in the 
blood is that of Romer. This depends upon the well-known fact 



Reaction of moderate severity seventy-two hours after the 

intracutaneous injection of one-fortieth the minimal lethal 

dose of diphtheria toxin. Patient's blood serum was found to 

contain no antitoxin (International Clinics). 


that the intracutaneous injection of toxin into guinea-pigs leads to 
localized necrosis in the course of forty-eight hours. The minimum 
amount of toxin sufficient to produce necrosis can be determined, 
the protective power of antitoxin determined, and subsequently 
with a standard antitoxin any new toxin may be titrated after the 
same general principles as described previously for antitoxin titra- 
tion. By this method the presence of toxin in human blood may be 
determined, inasmuch as normal human serum does not produce 
necrosis upon intracutaneous injection in the guinea-pig. 
Harriehausen and Wirth found that the serum from patients suffer- 
ing with diphtheria produced necrosis owing to the presence of 
toxin, and this was demonstrated in five cases for as long as thirty- 
five days after the onset of the disease. By the use of a titrated 
toxin the method may also be employed for determining the pres- 
ence and amount of antitoxin in human blood. 

Active Immunization Against Diphtheria. For many years im- 
munization to this disease was entirely in the form of passive im- 
munization, practised by giving protective doses of antitoxin. The 
antitoxin was given in doses of 500 to 1000 units and served to pro- 
tect for a period of about three to six weeks. This was of special 
importance in .institutions and families exposed to the disease. The 
disadvantages are the short period of immunity and the fact that 
the patient may thereby become hypersensitive to any subsequent 
injections of horse serum. Active immunity had been observed by 
Park in guinea-pigs which had been used for the titration of anti- 
toxin, and Park, in 1905, reported that horses treated with neutral- 
ized mixtures of toxin and antitoxin had produced immune sera as 
strong as 400 units per c.c. Theobald Smith suggested a similar 
method of immunization in man, and in 1913 von Behring reported 
the successful immunization of children and adults. The method 
of immunization with toxin and antitoxin mixtures has now attained 
a widespread use and is employed even as early as the fourth day of 
life. Active immunity of this sort is demonstrable by the Schick 
test in about ten days after treatment, and increases so that in the 
eighth week about 80 per cent, of the treated individuals are immune, 
by the twelfth week 96 per cent, are immune, and at the end of 
four months 98 per cent, are immune. According to Park, the re- 
maining 2 per cent, become immune if reinjected. The method of 
immunization is to give three injections subcutaneously one 
week apart. 

For the preparation of the mixture a ripe toxin is used and so diluted 
that I. c.c. will contain 200 minimum lethal doses as tested against gui^ea- 
pigs. This is slightly overneutralized with antitoxin and the mixture should 
cause no symptoms in guinea-pigs even when given in very large doses. As 
indicated above, antitoxin may deteriorate in the moist state, and this must 
be avoided in the toxin-antitoxin mixtures. If the mixtures are kept at about 
21 C. the mixture remains good for at least one year, although it is prefer- 
able to keep it at a lower temperature. The injection is given subcutaneously 
in the arm at the insertion of the deltoid muscle. The immunity developed 
following injection of this sort is against toxin, but vaccination against diph- 


theria bacilli themselves may also be practised at the same time by adding 
1000 millions killed organisms. The value of this latter procedure has not 
been demonstrated as yet and it is not widely practised. 

The advantage of the use of toxin-antitoxin mixtures is that a last- 
ing active immunity is established. It has been suggested, however, 
that the use of the antitoxin in the mixture may lead to the de- 
velopment of anaphylaxis. It has been maintained, on the other 
hand, that the mixture of the toxin probably avoids the sensitizing 
effect of the horse serum, but this is not borne out experimentally 
or in human medicine. Nevertheless, the amount of horse serum 
given is relatively small and the development of hypersusceptibility 
in man following these small amounts is not very common. Park 
has found that even with the therapeutic dose of diphtheria antitoxin 
the danger of anaphylaxis is extremely small, and states that 
among 330,000 cases on record there were only five deaths. As we, 
will point out subsequently (see page 230), the reports of deaths 
following antitoxin administration would indicate that, in a certain 
percentage at least, factors other than anaphylaxis are operative. 
If sensitiveness to horse serum is known it is suggested that anti- 
toxin prepared in some other animal, such as the goat, may be em- 
ployed, but sera of this sort are not easily obtainable in the market. 

Tetanus Toxin and Antitoxin. In the foregoing consideration 
much stress has been laid on diphtheria toxin and antitoxin, with 
the idea that the problem might thus be presented as simply as pos- 
sible. Tetanus toxin and antitoxin have been studied almost if not 
quite as intensively as diphtheria and deserve, both practically and 
theoretically, more than passing mention. The important facts may 
be given briefly. The toxic broth produced by growth of bacillus 
tetani contains a body which is actively hemolytic, tetanolysin, and 
more important, a body which produces the symptoms of tetanus, 
tetanospasmin. These are capable of specific absorption, so that 
one or the other remains free. In other words, the tetanolysin may 
be removed from the mixture by saturation with red blood-cor- 
puscles, leaving in the broth the tetanospasmin which may be in- 
jected with the production of symptoms and death. An antitoxin 
may be produced specifically for the tetanospasmin, but in practice 
the antitoxin is made without separation of the two toxins. 

The toxin is produced in anaerobic broth cultures. It is readily 
injured by heat and light, and is best preserved in the dried state. 
The white mouse is extremely susceptible, the guinea-pig less so 
and the horse somewhat less, whilst pigeons and fowl are highly 
resistant. The antitoxin is produced for commercial purposes in the 
horse, the earlier doses being with an attenuated toxin following a 
previous injection of antitoxin. The serum is standardized by the 
use of white mice or by guinea-pigs, the procedure being practically 
the same as for standardization of diphtheria antitoxin. In the 
United States the toxin is used as a standard. It is precipitated by 
ammonium sulphate and dried. The minimum lethal dose is that 


which kills a pig of 350 grams in four to five days. The antitoxic 
unit is ten times the amount of antitoxin necessary to protect 
against 100 minimum lethal doses. 

In man the symptoms appear, as a rule, first in trismus of the jaw 
muscles, but in experimental animals the first spasms are near the 
injection site when the toxin has been given subcutaneously or 
intramuscularly. For demonstration purposes the dried toxin is 
freshly dissolved and five minimum lethal doses injected into the 
thigh muscles of one hind leg of a guinea-pig. In the course of 
about two days the leg is found stiff and extended, the animal show- 
ing excitable reflexes. In the course of another day a sudden noise 
or other stimulus will excite convulsions, and later the animal will 
be found in tonic spasm and dies with all four extremities in exten- 
sion. If the toxin is given intravenously or intraperitoneally, the 
first symptoms are excitable reflexes, then general clonic and finally 
tonic spasm. If given intracerebrally, the onset is by epileptiform 
convulsions. Rabbits are much more resistant to the toxin, and 
an intravenous injection will lead to gradual wasting and a cachectic 
death, which has been called " tetanus sine tetano." The suscep- 
tibility of animals varies with the temperature of the body. Cold- 
blooded and hibernating animals are resistant at cold winter 
temperatures, but become susceptible at summer temperatures. 

Tetanolysin. The tetanolysin is easily demonstrable in a toxin. The best 
red blood-cells for use are those of the goat, sheep and horse. The fol- 
lowing protocol will show the method of titrating the tetanolysin. The toxin 
is dissolved so as to make a i per cent, solution in saline, and is further diluted 
for the experiment 1-2, 1-5, i-io, 1-20. The blood-cells are washed three 
times and suspended in salt solution so as to make a 5 per cent, solution. For 
method of washing red blood-cells see page 118. 






The mixtures are incubated in a water bath at 37 for one hour. 

The minimum lytic dose in the above instance is I c.c. of a 1-5 dilution of 
the i per cent, toxin solution. This is used as the unit to determine the 
antitetanolysin in an antitetanic horse serum as in the following protocol: 


5% sheep cells 

- Hemolysis 

1-2 (l.O C.C.) 

I.O C.C. 


1-5 (i.o c.c.) 

I.O C.C. 


I-IO (l.O C.C.) 

I.O C.C. 


1-20 (l.O C.C.) 

I.O C.C. 


Saline (1.0 c.c.) 

I.O C.C. 




Immune serum 

5% sheep cells* 



i.o c.c. 1-5 


I-I,OOO (l.O C.C.) 

I.O C.C. 



i.o c.c. 1-5 


1-2,000 (i.o c.c.) 

I.O C.C. 



i.o c.c. 1-5 


I-IO,OOO (l.O C.C.) 

I.O C.C. 



i.o c.c. 1-5 


1-20,000 (i.o c.c.) 

I.O C.C. 



i.o c.c. 1-5 


1-50,000 (i.o c.c.) 

I.O C.C. 


Normal horse serum 


i.o c.c. 1-5 


I-IOO (l.O C.C.) 

I.O C.C. 



i.o c.c. 1-5 


1-1,000 (i.o c.c.) 

I.O C.C. 



i.o c.c. 1-5 



I.O C.C. 




I-IOO (l.O C.C.) 

I.O C.C. 


*Add the sheep cells after the mixture of toxin and serum has been incubated for one-half 
hour and then incubate one hour. For method of diluting serum so as to obtain required 
strengths see page 84. 


Tubes 6-9 are controls to show that normal horse serum is not antilytic, 
that the laking dose still operates after the preliminary half-hour incubation, 
and that horse serum itself has no lytic effect. 

Tetanospasmin. For the demonstration of the neutralization of tetano- 
spasmin by antitoxin and by brain substance, the following experiments are 
of value. Five guinea-pigs of about 250 grams are needed. 

Pig No. i. Inject five minimum lethal doses of toxin into the thigh muscles. 

Pig No. 2. Mix ten minimum lethal doses of toxin with one unit of 
antitoxin. Allow to stand at room temperature for about twenty minutes 
and inject as in pig No. I. 

Pig No. 3. In a sterile mortar grind one-half the fresh cerebrum of a 
guinea-pig with five minimum lethal doses of toxin, adding salt solution in 
the smallest amount necessary. Allow to stand two hours, centrifuge and 
inject the supernatant fluid as in pig No. I. 

Pig No. 4. The other half of a guinea-pig brain is boiled for twenty 
minutes in water, then ground up with five minimum lethal doses of toxin, 
allowed to stand two hours, centrifuged, and the supernatant fluid injected 
as in pig No. i. 

Pig No. 5 serves as a control. 

The guinea-pig injected with toxin will show typical symptoms as de- 
scribed above, beginning with extension of the leg injected, then showing excita- 
ble reflexes followed by convulsions, tetanic spasm and death. The antitoxin 
and fresh brain substance will protect the animals, but the boiled brain will 
not. The normal animal serves best as a control for the elicitation of 
excitable reflexes and slight convulsions. 

Route of Absorption of Toxin. It is of interest to note that in 
man, horse, and guinea-pig the central nervous system alone has 
the power of neutralizing tetanus toxin, but in the case of the 
rabbit, liver and spleen in addition have this power. It is main- 
tained that the gray substance of the nervous system possesses 
this special affinity, and the white matter does not. Most authorities 
believe that the toxin is carried along nerve tracks, but Zupnik 
maintains that it travels through the blood stream and is found not 
only in the nervous system, but also in the muscles. Studies of 
Meyer and Ransom and of Marie and Teale indicate that both 
routes are followed. Depending on the size of the dose, the site of 
inoculation, and perhaps certain other factors, one or the other 
route may be followed predominantly, but never to the exclusion of 
the other. According to Teale and Embleton, the mode of transit 
along nerve trunks is by way of the axis cylinders and the peri- 
neural lymphatic vessels. These authors, however, maintain that 
toxin cannot pass from the choroidal plexis into the cerebrospinal 
fluid, nor from the capillaries of the central nervous system to the 
nerve tissues. The special affinity of tetanospasmin for nerve sub- 
stance is not peculiar and is also exhibited by the neurotoxins of 
snake venom and by the toxin of bacillus botulinus. Teale and 
Embleton believe that tetanus antitoxin does not enter the sub- 
stance of the central nervous system following either intravenous or 
intrathecal injection, but simply acts by neutralization of the toxin 
at the site of formation. Clinical experience is not entirely in 
agreement with the experimental work of these authors, since cases 
have been improved by the use of serum after tetanic spasms 
have appeared. 

Therapeutic Use of Tetanus Antitoxin. As is well known, tetanus 


follows the introduction of the bacilli or their spores into wounds in 
such a fashion that anaerobic growth is permitted. The incubation 
period is usually considered to be eight days, but there are many 
variations from this standard period, including cases that have an 
incubation period of over sixty days. The mortality from the dis- 
ease is extremely high, the average ranging between 78 and 90 per 
cent. Its incidence in civil life is not very great, but in time of war 
it is likely to occur with considerable frequency because of the con- 
tamination of war wounds by soil containing the organism or its 
spores. In the American Civil War the disease occurred in 2.5 per 
cent, of the wounded; in the Franco-Prussian War in 3.5 per cent.; 
and in the World War 6.5 per cent. In the earlier wars the mortality 
ranged between 80 and 90 per cent., but in the World War, owing 
in all probability to prophylaxis and treatment, the mortality was 
50 per cent. In carefully studied statistics it is found that the longer 
the incubation period the lower is the rate of mortality. This general 
statement held true before the use of anti-tetanic serum was instituted 
and still holds true. The difference between the mortality rate of 
80 to 90 per cent, in the earlier wars and 50 per cent, in the World 
War gives an excellent illustration of the decrease in mortality that 
has followed the introduction of serum prophylaxis and treatment 
as well as rational surgery. Knowing that the organism is anaerobic 
in growth, surgery demands that contaminated wounds be kept open 
for the access of air. 

Prophylactic Use of Serum. The use of tetanus antitoxin is 
directed toward prophylaxis and toward cure. As can readily be 
understood from the experiments outlined above, the toxin of this 
disease is very firmly bound to nerve tissues ; therefore, treatment 
established after the disease has appeared is not likely to be so 
effective as in the use of some other antitoxins. Nevertheless, not- 
able success has been attained in some cases where the disease has 
become well advanced before serum treatment has been instituted. 
Prophylactic treatment with serum is given as early after the 
wound as possible, and in both military and civil life all wounds 
contaminated with soil should receive protective doses of tetanus 
antitoxin. This is given subcutaneously in doses of 500 to 1000 
units. Wolff reported that in the German army prior to December, 
1914, prophylactic injections were not regularly given and the inci- 
dence of tetanus amounted to 1.4 per cent, of the wounded. During 
the following seven months prophylactic injections were given in 
the field to all those wounded. by grenades and shrapnel, but not 
those wounded by rifle bullets, and the incidence of the disease was 
reduced to 0.16 per cent. Protection was equally as successful in 
the Allied armies, and instructions were given to administer serum 
as soon after injury as possible, either in the first-aid station or in 
the field hospitals. Experiences in the British army demonstrated 
that cases might develop a considerable time after the wound was 
inflicted, and for this reason subsequent orders directed the use of 


500 units of tetanus antitoxin every ten days for four doses. It was 
further recommended that the serum be given subcutaneously not 
more than seven days and not less than two days before any oper- 
ative procedure upon an old wound. If haste is necessary the serum 
may be given intramuscularly twelve hours before operation. Ob- 
viously this suggests the possibility that organisms may remain 
dormant in wounds, to become active at a later period ; it is further be- 
lieved that the antitoxin is probably eliminated in about ten days, 
and the later doses of immune serum are given in order to neutral- 
ize any toxin that might be produced subsequently. 

Golla tabulated the following cases not receiving prophylactic 
doses of antitoxin: 

Incubation period Cases Mortality 

i- 7 days 17 (32.7 per cent.) 82.5 per cent. 

8-14 days 24 (46.2 per cent.) 79.0 per cent. 

15-21 days 6 (11.5 per cent.) 54.0 per cent. 

Over 21 days ' 5(9-6 per cent.) 

This shows that the commonest incubation period is eight to 
fourteen days, and also illustrates the fact that the shorter the incu- 
bation period the more serious is the disease. In another series of 
patients who had received prophylactic treatment with serum, the 
following data were collected ; 

Incubation period Cases Mortality 

i- 7 days 61 (22.6 per cent.) 75.5 per cent 

8-14 days 93 (34.6 per cent.) 70.0 per cent. 

15-21 days 33 (12.2 per cent.) 60.8 per cent. 

21-30 days 19 (7.05 per cent.) 62.8 per cent. 

30-40 days 14 ( 5.2 per cent.) 57.0 per cent. 

40-50 days 9 ( 3.3 per cent.) 33.4 per cent. 

50-60 days 18 ( 6.7 per cent.) 27.7 per cent. 

Over 60 days 22 ( 8.2 per cent.) 40.8 per cent. 

In the Franco-Prussian War only 5.7 per cent, exhibited an in- 
cubation period of more than twenty-one days, whereas, according 
to Golla, in the last war 30.54 per cent, showed an incubation period 
of more than twenty-one days. In summary it may be stated that 
the introduction of prophylactic injections of the tetanus antitoxin 
not only reduces the incidence of the disease, but also lengthens 
the incubation period, and therefore reduces the mortality. The 
delay in incubation usually leads to more moderate symptoms as 
well as reduces mortality, and oftentimes the cases exhibit tetanic 
spasms in only one extremity. 

Treatment of Tetanus with Serum. When the disease has de- 
veloped, treatment must be prosecuted vigorously. In the earlier 
years of its employment subcutaneous, intramuscular, and intra- 
venous administration was practised, but arguing from the nature of 
the disease it was soon suggested that intrathecal injections be given. 
This suggestion was followed by experimental and clinical investi- 
gation, and in the hands of the majority of workers the method has 
been found to have great value. Park and Nicoll injected twice the 


fatal dose of toxin into the hind legs of guinea-pigs and seventeen 
to twenty-four hours subsequently injected antitoxin by various 
routes. Six animals receiving the immune serum subcutaneously 
died ; fifteen received it intracardially and two survived, whereas 
sixteen animals received it intrathecally and thirteen survived. It 
was found that the dose necessary for intrathecal injection was con- 
siderably smaller than the dose necessary for injection into the cir- 
culation. Sherrington conducted a similar series of experiments 
upon monkeys with essentially the same results. He used twenty- 
five monkeys for his series of injections and the following table 
gives the results : 

Time between 

Route of injection giving of toxin Recoveries Deaths 

and antitoxin 

Lumbar intrathecal 47-78 hours 14 1 1 

Bulbar intrathecal 47-78 hours 13 12 

Intravenous 47~78 hours 7 18 

Intramuscular 47-78 hours 3 22 

Subcutaneous 47-78 hours 2 23 

Cerebral subdural, ten cases 47~78 hours o 10 

Clinically Irons was not able to demonstrate such a marked dif- 
ference in results, and Leishman and Smallman came to the conclu- 
sion that the intramuscular route is the best. The work of Andrew 
and Golla demonstrated the clinical value of the intrathecal method. 
Experimental work also shows that although antitoxin can take up 
toxin after fixation with nerve tissue, such a release of toxin is re- 
stricted by long contact with the nerve tissue. This explains the 
necessity for early administration of antitoxin. For example, the 
experiments of Doenitz show that the amount of antitoxin neces- 
sary for protection increases tremendously with a lapse of time. 
He injected twelve times the fatal doses of toxin and found that 
after the lapse of four minutes a slight excess of antitoxin was suffi- 
cient to protect the animal, but after eight minutes six times this 
dose of antitoxin was required ; after sixteen minutes twelve times 
the dose, after 1 hour twenty-four times the dose; in four to six 
hours six hundred times the original dose, and after six hours he 
was unable to save the animals. As a result of long experience with 
treatment it has finally been determined that a combination of 
modes of injection is desirable in order to procure complete and 
lasting saturation of the body with antitoxin. When giving intra- 
thecal injections it is well to draw off the spinal fluid and then 
immediately inject 3000 to 5000 units of toxin, diluting the serum 
to a volume of 10 to 15 c.c. with sterile salt solution. Where no 
fluid can be withdrawn from the spinal canal the antitoxin is intro- 
duced very slowly by gravity. The intrathecal injection is further 
supplemented by 10,000 to 15,000 units intravenously, and three to 
four days later a similar injection subcutaneously. It is often ad- 
visable to repeat the intrathecal injections each day for three or 
four days. The following outline taken from the Memorandum 


on Tetanus published by the British War Office gives a plan for 
combined injections in a case of acute tetanus; 

Day Subcutaneous Intramuscular Intrathecal 

First 8,000 units 16,000 units 

Second 8,000 units 16,000 units 

Third 4,000 units 8,000 units 

Fourth 4,000 units 8,000 units 

Fifth 2,000 units 

Seventh 2,000 units 

Ninth 2,000 units 

This outline is offered as a suggestion for treatment and has 
been applied successfully. The doses are arranged in multiples of 
8000 because that was the size phial issued in the British army. 
Doses may be varied, but it is strongly advised to administer a 
total of 75,000 to 100,000 units. In those cases with long incuba- 
tion period the dose may be smaller, and if the case is one of spasm 
in one extremity, without evidence of involvement of higher centers, 
such as spasm of jaw muscles (trismus), the serum may be given 
by intramuscular and subcutaneous routes in amounts of 3000 to 
6000 units. The patient should be placed so that he lies with the 
feet considerably higher than the head, so as to allow drainage to- 
ward the head. It has also been suggested that the antitoxin be 
applied near or in the wound. Calmette recommended that pow- 
dered antitoxic serum be applied locally. Suter recommended rub- 
bing the fluid serum into the wound. Bockenheimer recommended 
that it be introduced in the form of ointment, and Robertson satur- 
ated pads of cotton with antitoxin, dried these for twenty-four hours 
at 40 to 45 C., and applied them locally. As will be seen, these 
latter measures are probably more in the nature of prophylaxis than 
treatment, and no definite information has accrued as to their value. 
The disadvantages of serum treatment are essentially the same as 
those in the use of diphtheria antitoxin, but in addition we have to 
deal with the factor of introduction of foreign serum into the spinal 
canal. This frequently leads to the development of a sterile menin- 
gitis with a formation of purulent fluid. As far as can be learned, 
this inflammation does no damage. A few reports of nerve and 
cord lesions following the use of antitetanus serum intrathecally 
have been reported, but they are extremely small in number com- 
pared to the number of cases treated, and it would appear that the 
high percentage of mortality in this disease justifies the intrathecal 
treatment in spite of the minor element of danger. 

Dysentery Toxin and Antitoxin. Dysentery toxin may be pro- 
duced in broth by the growth of the Shiga bacillus. It is probable 
that the Flexner and Hiss-Russell types produce only an endotoxin. 
This is consistent with the greater clinical and pathological severity 
of the Shiga type of dysentery. The broth must be definitely alka- 
line, the optimum stated by Doerr being reached where 0.3 per cent, 
soda is added to a broth neutral to litmus. Rabbits are very sus- 
ceptible and the intravenous injection of a filtered toxin broth in 


proper doses will produce marked, often bloody, diarrhea, wasting, 
paresis, or even paralysis of extremities, and death. The autopsy 
shows marked inflammation, often hemorrhagic, particularly severe 
in the cecum, but also involving the large intestine and lower 
ileum. Monkeys, cats, and dogs are also susceptible, but fowl, pigeons, 
and guinea-pigs are resistant. Antitoxin can be produced in horses 
and goats. There is considerable difficulty in standardizing such a 
serum, owing to the variation in individual susceptibility of ani- 
mals. Kraus and Doerr have shown that the immune serum first 
shows a capacity to neutralize toxin in vitro, then in vivo (simul- 
taneous injection of toxin and antitoxin into opposite ear veins), 
and finally it attains a definite curative value as demonstrated by 
primary injections of toxin followed after certain time intervals by 
antitoxin. A serum must have a high curative value before it is 
acceptable and is used in doses of cubic centimeters rather 
than units. 

Therapeutic Use of Anti-dysentery Sera. After the discovery of 
the dysentery bacillus by Shiga in 1898 it was found that the sepa- 
rate types of this organism vary greatly in their power to produce 
toxic substances. The most toxic varieties are those of Shiga and 
Kruse, and their toxins are not only endotoxic but also exotoxic in 
nature, a fact clearly established by the work of Todd, Liidke, 
Kraus, Doerr, and Rosenthal. Shiga was the first to immunize 
horses with killed cultures of his organism and produced highly 
protective sera capable of saving guinea-pigs injected with six 
times the lethal dose of living bacilli. This specific anti-bacterial 
serum was used by Shiga with encouraging results during a dysen- 
tery epidemic in Japan, the mortality among cases treated with 
Shiga's serum being one-third of that among cases treated by the 
usual routine procedures. Not only was the mortality greatly re- 
duced, but the total period of illness decreased from forty to twenty- 
five days. A similar serum was prepared by Kruse and its use 
reduced the mortality among Kruse's cases from n to 5 per cent. 
Kraus and Doerr also obtained favorable results from the use of 
their serum, which was mainly an antitoxic serum produced by the 
injection of filtrates of young cultures into horses. Vaillard and 
Dopter treated a large number of cases with a serum prepared by 
themselves and possessing both antibacterial and antitoxic prop- 
erties and reported highly encouraging results with a mortality of 
2 per cent., while the mortality otherwise would have been between 
ii and 25 per cent. More prompt effects were obtained when the 
serum was given at the earliest moment in the course of the disease. 
Vaillard and Dopter used 20 to 30 c.c. in moderate cases and from 
40 to 80 c.c. in grave cases. In late cases serum injections were 
often of value. Graham more recently has added a valuable contri- 
bution to the serum therapy in bacillary dysentery, his studies being 
made during the campaign in Macedonia. Graham used a serum 
prepared at the Lister Institute and gave intravenous injections of 


60 to 80 c.c. once or twice daily during the first three days of treat- 
ment. Three injections were followed by 150 to 300 c.c. of saline 
daily for the first two days and once for the next two days, the 
saline injections being made to prevent dehydration of the tissues. 
In mild cases no saline injections were necessary. Most of the cases 
arrived after the third day, so that they were not placed under 
treatment at the earliest possible moment. On entering the hos- 
pital all cases received 20 c.c. of the serum subcutaneously. Klein 
also maintains that anti-dysenteric serum given early and in large 
doses intravenously (60 to 100 c.c.) is efficacious. He found that the 
use of the serum produced the best results when given during the 
first five or six days. When the disease has entered into the inter- 
mediate stage, from the sixth to the tenth day, the outcome of the 
disease is irrespective of serum treatment. In the third stage 
tenth day the use of serum is practically without value. Waller 
treated 140 cases with the Lister Institute serum and found that 
the early use of the serum resulted in shortening the duration of the 
disease. He gave three subcutaneous injections of 140 c.c. at eight- 
hour intervals during the first twenty-four hours to fairly severe 
cases. Rosenthal, in a series of serum-treated cases, found a mor- 
tality of 0.6 per cent. In other units the mortality was 10 to 15 per 
cent. Sixty c.c. of sera were given by Rosenthal on the first day, 
followed by 40 to 60 c.c. on the second, and if no improvement was 
observed subsequent doses of 40 c.c. were given up to a 
total of 400 c.c. Usually the stools were free of blood in forty-eight 
hours, and their number reduced from 60 to 15 or 10 per day. 
Lantin also thinks that the use of serum constitutes an efficient 
specific method of treatment. He gave the serum by rectum in doses 
from 30 to 50 c.c. Neumann used human convalescent serum in 400 
cases. Intestinal irrigations with silver solutions were also em- 
ployed by this author. Only six of his cases ended fatally. Jacob, 
on the other hand, and with him also Nolf, failed to obtain success 
with serum therapy in this disease. Jacob treated ninety cases, 
using polyvalent sera and injecting subcutaneously or intravenously 
doses ranging from 20 to 400 c.c. during the first or second week of 
the disease. According to the British Medical Research Com- 
mittee, serum treatment of bacillary dysentery is not satisfactory. 
Nevertheless, numerous investigators showed that this method of 
treatment has a well-established clinical value as expressed in the 
view of Schittenhelm, who states that it should be employed in all 
cases of more than three or four days' duration, and in all cases 
showing toxemia and severe symptoms, and in cases where the 
number of stools are more than twelve in the course of twenty-four 
hours. It should be given early in the disease and in massive doses. 
If possible the type of the infecting organism should be known prior 
to the administration of these massive doses. This can readily be 
done in twenty-four hours in a well-equipped laboratory. The 
serum used should be polyvalent, because there are a number of 


serologically distinct types of dysentery bacilli. Schmitz, for in- 
stance, found in a dysentery outbreak among prisoners of war in 
Roumania strains which resembled the Shiga bacillus but were 
serologically entirely distinct types. Pribram also found that an 
antitoxin specific for the Shiga-Kruse toxin is inactive toward the 
toxin of a strain D 118 H (Hallmann). Furthermore, the curative 
action of anti-dysentery serum is due first to its content in antitoxin, 
and second to its anti-bacterial properties. 

The serum can further be employed for prophylactic injections in 
doses from 10 to 30 c.c., but the immunity thus produced will be only 
of a short duration. Recently Boehneke and Elkeles have inocu- 
lated over 100,000 persons with a polyvalent bacillary toxin-anti- 
toxin preparation called dys-bakta, but complete protection was not 
secured. It was noted, however, that infections occurring in the 
inoculated individuals were usually of slight severity, and death a 
very unusual occurrence. The reaction following inoculations was 
no more severe than that following typhoid inoculations. Immunity 
thus produced lasted for at least three months. 

Botulinus Toxin and Antitoxin. Bacillus botulinus produces a 
toxic body leading to symptoms often called " ptomaine poisoning." 
The toxin, however, is apparently independent of the medium used, 
is destroyed by moist heat of 58 C. for three hours, and of 80 C. 
for one-half hour, and is capable of inducing the formation of an 
antitoxin. The symptoms produced by the toxin are marked in- 
crease or decrease of saliva flow, vomiting, sometimes diarrhea, 
but more often constipation, often retention of urine, paralysis of 
eye muscles, aphoria, rarely fever or disturbance of sensitivity. 
Death frequently ensues following the appearance of symptoms of 
bulbar paralysis with disturbances of respiration and heart action. 
The necropsy shows marked general passive congestion and throm- 
bosis of the meningeal vessels sometimes with slight hemorrhage. 
Unlike other toxins, that of botulism resists the digestive juices and 
is absorbed by way of the alimentary canal. It can be neutralized 
by brain substance and by the lipoids, lecithin, cholesterol, and by 
fats, such as butter and oil. It is toxic for man, monkey, cat, rabbit, 
and guinea-pig. 

The Use of Immune Sera in Botulism. Van Ermengem in 1895 
discovered the cause of botulism poisoning to be an exotoxin pro- 
duced by a strictly anaerobic Gram-positive bacillus which he iso- 
lated from portions of a ham that had caused fifty cases of poisoning 
at Ellezelles, Belgium^ The disease has an exceptionally high mor- 
tality of almost loo per cent., and up to the present time the per- 
centage of fatal cases has been as great as it was fifty years 
ago. The reason for this lies in the fact that the early symptoms of 
the disease are not recognized until the toxemia is well established. 
In the year 1897 Kempner showed that susceptible animals may be 
successfully immunized to the toxins of this organism and obtained 
a potent antitoxin from goats, I c.c. of the serum protecting against 



100,000 minimal lethal doses. Forssman and Lundstrom were also 
successful in their immunization attempts, using attenuated toxins. 
Wassermann immunized horses and produced sera of undeniable 
value in animal experiments. In this country sera were prepared 
by Graham, Brueckner and Pontius, Buckley, Hart, Meyer, Hurwitz 
and Taussig, Burke, Dickson, and Howitt mainly for experimental 
purposes, using rabbits, sheep, goat, cattle, and dogs for immuniza- 
tion. According to Dickson and Howitt, laboratory experiments 
show that the antitoxin may protect against the action of the toxin 
for at least twenty-four hours after the administration of one test 
dose of toxin, but the effectiveness is, to a certain extent at least, 
dependent upon the amount of toxin injected. Like tetanus anti- 
toxin, botulinus antitoxin should be given early if it is to be effec- 
tive, and even in well-established cases it is strongly advisable to 
give antitoxin in massive doses, because Kob has demonstrated that 
this toxin may persist in the blood nine days after the poisoning. 
If symptoms of botulism, such as hypersecretion of mucus from 
mouth and nose, visual disturbances, aphonia, dysphagia, and 
paralysis of the intestinal tract appear, antitoxin should be admin- 
istered as soon as possible, and should be given in large doses 
intravenously. Dickson also advises the use of antitoxin to all 
persons who have eaten fowl that have suffered from limberneck. 
Of importance is the use of polyvalent sera because of the discovery 
of Leuchs that two strains, the one of Van Ermengem and a 
Darmstadt strain, were distinct, that the toxin of one was not 
affected by the specific antitoxin of the other, and vice versa. As 
for the effect of botulinus antitoxin in man, little is known, as it 
has been used only in isolated instances. Dickson and Howitt, in 
1918, gave 85 c.c. of immune goat serum (i c.c. equivalent to 3000 
M.L.D. for a guinea-pig) to each of two patients at Madera, Cali- 
fornia. Both patients recovered, but as the antitoxin was given very 
late, in fact, after all the more seriously poisoned patients had 
succumbed, there is no definite evidence that the course of the ill- 
ness was favorably influenced by the antitoxin, although it was 
later shown that the toxin of the strain recovered from the food was 
Type A. McCaskey used small doses of antitoxin in three patients 
(5 to 10 c.c.). One died and two recovered and this author there- 
fore thinks the serum to be of some aid. Nonnenbruch obtained 
rapid improvement in his case after the use of antitoxin. His pa- 
tient became poisoned after eating sausage. Jennings, Haas and 
Jennings in the recent Detroit outbreak used Graham's serum in a 
dose of 42 c.c. intravenously in one case without apparent effect, and 
20 c.c. in two injections to another patient, who recovered, and state 
that the latter case was not of mild type. Dickson and Howitt 
found that of all the outbreaks in which the serum had been used, 
with the exception of the cases of McCaskey, the toxin was that of 
Type A, and consequently when Type B serum was used it could 
not be expected to give any satisfactory results. As it is impos- 


sible to determine quickly the type of toxin in a particular outbreak, 
it is of the greatest importance to use polyvalent sera. 

Gas Bacillus Toxin. The frequent occurrence of gas gangrene 
in the Great War has given especial interest to the preparation of 
antitoxins for the organisms causing the disease. Klose, in 1916, 
and Bull and Pritchett, in 1917, were able to prepare a soluble toxin 
of the bacillus Welchii or as it is often named bacillus perfringens. 
Bull and Pritchett drew especial attention to the necessity for select- 
ing a strain which is capable of producing toxin in fairly large 
amounts. The British Medical Research Committee reports that 
the toxin of vibrion septique has very little effect following 
subcutaneous injection. Upon intravenous injection, however, it 
produces convulsions and usually death in a few minutes. An 
antitoxin may be produced, but it is not effective after the toxin has 
been injected. The toxin of bacillus edematiens produces massive 
edema about the site of inoculation. The toxin of bacillus aerogenes 
capsulatus was found to have a necrotic action upon the tissues ; it is 
generally toxic in large doses and animals may be protected by 
antitoxic serum. 

The Use of Immune Sera in Gas Gangrene Treatment of the 
Disease. Leclainche and Vallee, Sacquepee, Weinberg and Seguin, 
Bull and Pritchett were the first to apply serum therapy in wounds 
infected with the gas bacilli. Leclainche arid Vallee's and Weinberg 
and Seguin's serums were polyvalent and also antibacterial, while 
Bull and Pritchett's serum was antitoxic. In 1917 Bull and 
Pritchett produced an exotoxin from twenty-four-hour cultures of 
bacillus aerogenes capsulatus, which when injected into pigeons 
or guinea-pigs caused local edema, necrosis, and hemolysis of red 
cells, and was capable of stimulating the formation of an antitoxin. 
Bull's claim for the potency of his antitoxic serum was based on ex- 
periments in which he used pure cultures of bacillus aerogenes cap- 
sulatus and made no attempt to discriminate between the different 
types of the organism, such as have been found to exist by Henry, 
or to consider the fact that in war wounds the bacillus aerogenes 
capsulatus is not the only causal factor of gas gangrene. From 
Nevin's work it would appear that neither anti-perfringens serum 
(bacillus aerogenes capsulatus anti-microbial serum) nor Bull's anti- 
toxin afford any protection when other pathogenic anaerobes inci- 
dent to war wounds are present, together with bacillus aerogenes 
capsulatus, whereas when the vibrion septique and bacillus 
edematiens are present in mixed infections without bacillus aero- 
genes capsulatus, the prophylactic use of the specific sera, even 
when diluted by another serum, is effective. Weinberg and Seguin, 
who have contributed extensively to the serum therapy of gas 
gangrene, found treatment by serum alone limited because of rapid 
absorption of toxin in this disease. The association of rational 
surgery and of serum therapy gives the best results. In a series of 
sixty-six cases reported by these authors in which sixty did not 


receive serum treatment, three received non-specific treatment and 
three suffered complications, thirty-five deaths were recorded, while 
in a series of twenty-four specifically treated cases only five deaths 
occurred, thus reducing the mortality from more than 55 per cent, 
to less than 21 per cent. The serum used in these cases was poly- 
valent, produced against bacillus aerogenes capsulatus, the vibrion 
septique, and bacillus edematiens. Duval and Vaucher, in 1917, 
reported fifty cases in which a combination anti-perfringens, anti- 
edematiens, and anti-vibrion septique serum prepared by Weinberg 
and Seguin was injected prophylactically. In none of these patients 
did gas gangrene develop, although all were of the most severely 
wounded type. Twenty-five died as a result of severe multiple 
wounds without any signs or symptoms of gas gangrene. 

Prophylactic Use of Sera. A year later these same authors re- 
ported a series of 281 cases in which severely wounded patients 
were injected with polyvalent serum prepared at the Pasteur Insti- 
tute. Eighteen developed gas gangrene (6.4 per cent.), and of these 
ten died, resulting in a mortality of 3.5 per cent., the usual mortality 
from gas gangrene in severely wounded being 16 per cent. Mairesse 
and Regnier found among 1016 wounded men examined bacteriologi- 
cally 297 gas bacillus infections. They received prophylactic injec- 
tions of anti-serum depending on the type of organism present. In 
thirty instances, or 10 per cent, of the cases, the disease developed. 
Ivens also used Weinberg and Seguin's serum in 222 cases for 
prophylactic injections. Among these no deaths occurred, and 
fourteen amputations were performed without fatal results. With 
Leclainche and Vallee's serum (154 cases) four died, and in fifty- 
seven other cases treated with both sera two deaths occurred. 
Further favorable reports were made by Quenu, Bazy and Routier, 
Vincent and Stodel, Marquis, Dufour and Samelaigne. Curative 
injections were given by Duval and Vaucher with 20.7 mortality. 
Rouvillois, Guillaume, Louis, Pedeprade, and Thibierge treated 
twenty-five cases, five of whom died. Of these three were moribund 
on entrance to the hospital. Mairesse and Regnier's thirty treated 
cases had a mortality of 16.6 per cent. 

Van Beuren, who reports a personal communication from Lieut.- 
Col. W. Elser, states that prophylactic doses were given to 15,000 
soldiers and controlled by 15,000 others. According to this finding 
there was not sufficient difference in the incidence rate to warrant 
any definite declaration as to the protective value of the sera used. 
Apparently these investigators were favorably impressed; for they 
laid the failure to secure better results to the weakness of the 
serum then available. Elser advises the following routine for the 
serum treatment: 

1. A prophylactic dose of polyvalent serum, combined with 
tetanus antitoxin, given as early as possible after the receipt of 
the wound. 

2. Bacteriologic examination of the wound and establishment of 


the presence of gas bacillus infection and determination of the 
variety of the bacteria. 

3. Administration of specific serum, either single or polyvalent 
or " pooled," according as there are one or more gas formers found, 
and also the administration of anti-streptococcus serum, since the 
latter organism is very commonly found in association with the 
other organisms. 

From the general reports obtained during the Great War it is 
considered that intravenous injection is to be preferred, in combina- 
tion with deep muscular injections in the vicinity of the wound. 
From these reports it seems, then, that the use of a polyvalent anti- 
bacterial and antitoxic serum is advisable, but much work on the 
subject must yet be done. From all the observations at hand it is 
safe to state that the best results are to be obtained from 
preventive injections. 

Bacterial Hemotoxins. As an example of the hemotoxins pro- 
duced by bacteria certain details of staphylolysin may be consid- 
ered. The hemotoxin is produced by twelve to thirteen days' 
growth of staphylococcus pyogenes aureus or albus in broth. The 
organisms are killed and the broth filtered through a porcelain 
filter. The filtrate can be preserved by the addition of 5 per cent, of 
a solution made up of 10 parts phenol, 20 parts glycerol, and 70 parts 
water. Doses of 0.025 to 0.05 c.c. should completely hemolyze one 
drop of rabbit blood after two hours at 37 C. Antilysin may be 
produced by immunization of animals and is found normally to a 
slight extent in normal human blood and in that of certain lower 
animals. The victims of staphylococcus infections frequently show 
an increased antilysin content of the serum. This fact has been em- 
ployed by Bruck, Michaelis, and Schultze to diagnose staphylococcus 
infections, some cases showing increases of ten to one hundred times 
over the normal antilysin. The simplicity of bacteriological exami- 
nation, however, makes this method of diagnosis by comparison 
rather cumbersome and time consuming. Whether or not antilytic 
sera would be of value in the treatment of those cases that resist or 
are unsuitable for vaccine treatment has not been determined so far 
as we have been able to learn. 


Introduction. Although literally the phytotoxins include all the 
toxins of vegetable origin the term usually is restricted to include 
those originating in forms of vegetable life higher than the bacteria. 
With this definition thought would be first directed to the poison- 
ous fungi, but as has already been shown, only one of the poisons so 
far isolated is capable of inducing antibody formation. The poison- 
ous elements of poison ivy and poison oak produce no antibodies. 
The poisonous elements of those plants that produce " hay fever " 
require separate discussion, because the toxic factor operates only 
on individuals who show a peculiar susceptibility or " hypersus- 


ceptibility." The element of hypersusceptibility in this connection 
will be deferred until after the presentation of the fundamental 
material on anaphylaxis and hypersusceptibility. The following 
paragraphs will present briefly the essentials concerning ricin, abrin, 
robin, crotin, curcin, and phasin. This brevity is justified by the rela- 
tively small practical importance of these substances. 

Ricin is the toxic principle of the castor-oil bean, ricinus com- 
niunis. It was isolated by Gibson in 1887 and named ricin by 
Stillmark in 1888. Gushing made very strong toxic preparations and 
Field states that ricin will kill rabbits in doses of o.oooi mg. per 
kilo ; guinea-pigs, 0.0008 mg. ; dogs, 0.0006 mg. ; cats, 0.0002 mg. ; and 
goats, 0.003 mg. Following injection there is an incubation period 
succeeded by diarrhea, somnolence, weakness of extremities, and 
death. At the necropsy are found reddening and swelling of Peyer's 
patches, mesenteric and retinal hemorrhages, ulcers of stomach, 
nephritis, general lymphatic swelling, and softening and degenera- 
tion of the pyramidal cells of the cerebral cortex. Beauvisage re- 
ported 150 cases of ricin poisoning in man of which nine were fatal. 
Many of these were children who ate the seeds, but there were also 
soap makers who handled the beans in soap manufactories. Ricin 
and the other toxins in the group may be precipitated with the pro- 
teins by ammonium sulphate ; they are precipitated by alcohol and are 
gradually destroyed by proteolytic enzymes. Jacoby, however, 
claims to have produced ricin and abrin which failed to give pro- 
tein reactions. Osborne, Mendel, and Harris maintain that ricin is 
inseparably associated with protein, and that Jacoby's error was 
due in all probability to the fact that he obtained a product so toxic 
that the small amounts necessary for toxic action were too small to 
give the protein reactions. The most striking character of ricin in 
vitro is its capacity to agglutinate the red blood-corpuscles of prac- 
tically all warm-blooded animals. It may agglutinate other body 
cells, precipitates protein, and is adsorbed by casein, fibrin, coagu- 
lated serum albumin, and by silk. Jacoby concludes that ricin is a 
mixture of agglutinin and toxin, the two having certain molecular 
groups in common. Ehrlich believes that these may undergo altera- 
tion into agglutinoid and toxoid. The mechanism of the agglutina- 
tion is not clear and many hypotheses, none quite satisfactory, have 
been advanced. Ehrlich produced an antiricin by giving increasing 
doses to animals by mouth, and then changing to subcutaneous in- 
jections. This antiricin was used by Ehrlich in the development of 
much of his hypothesis of the toxin antitoxin union because of the 
ease of manipulation as compared with the time-consuming and 
expensive method of working with animal injections of toxin anti- 
toxin mixtures. In addition to the antitoxin there are present in the 
serum a closely related antiagglutinin (with which Ehrlich worked) 
and a precipitin for ricin solutions. 

Abrin is obtained from paternoster or jequirity bean, abrus pre- 
catorius, and was described by Warden and Waddell in 1884. It is 


much less toxic than ricin, producing gastro-enteritis, hemorrhages, 
and swelling of lymph-nodes. Local applications led to an acute 
conjunctivitis and in hairy regions to transitory loss of hair, both 
of which may be protected against by immunization. Robert states 
that in India and Ceylon cattle were immunized (by feeding beans) 
against the effects of wounds by abrin-coated projectiles. Roemer 
found that by repeated application to the conjunctival sac of one 
eye, he could produce an immunity which first protected that eye 
and, after further immunization, served to protect the opposite 
untreated eye, in this later stage becoming a general immunity with 
antiabrin in the serum. Abrin is also a hemagglutinating agent, 
and can be distinguished from ricin by immunological experiment. 
In many respects abrin and its immunity resemble ricin very closely. 

Crotin is derived from croton seed, croton tiglium, and is less 
toxic than either ricin or abrin. According to Elfstrand, it agglu- 
tinates the red blood-corpuscles of beef, sheep, swine, and frog; it 
hemolyzes the cells of rabbit, cat, and crow, and has no effect on the 
erythrocytes of man, dog, guinea-pig, rat, hen, goose, and pigeon. 
Immune sera can be produced by the usual methods. Jacoby found 
in Grubler's pepsin a body which he called pseudo-anticrotin, cap- 
able of neutralizing the action of crotin on erythrocytes in vitro but 
not in vivo, and he found the same substance in gastric and 
intestinal mucosa. 

Cwrcin is produced from the seeds of jatropha curcus, and robin 
from the leaves and bark of robinia pseudacacia. Immune sera can 
be produced against both of these. 

Phasin is a name given by Landsteiner and Raubitschek to a 
hemagglutinating substance found in the seeds of the bean, pea, 
lentil, and vetsch. Antiagglutinins are found in normal serum and 
may be increased experimentally, but this substance or group of 
substances can hardly be regarded as belonging to the class of 
toxins because of little or no toxic symptoms following injection. 

Pollen Proteins or Pollen Toxin. The modern studies of hay 
fever and of asthma place this subject so clearly in the group of 
anaphylactic phenomena that its consideration is deferred (see 
page 233). 


Introduction. The zootoxins include the poisonous elements 
produced in animal life. They may be, and most frequently are, in 
the form of excretions of special poison glands or are found in secre- 
tions of other glands, in blood and in tissues. The most important 
are the snake poisons, but there are also included the poisons of 
spiders, scorpions, bees, centipedes, tarantula, toads, poisonous fish, 
duck-bill platypus, and the sera of various animals. 

The snake venoms differ somewhat in their action according to 
family, the colubridae, including the cobra, Australian black snake, 
and others ; the viperidse, including the European viper and Ameri- 


can rattlesnake ; and the hydrophinae or poisonous sea snakes. The 
venoms secreted by special glands are injected during the bite 
through fine canals in the fangs (not the forked tongue), and are 
all hemolytic. The fact that the blood of snakes contains poisons 
similar to those of the venom indicates that the poison glands 
secrete with little alteration the poison of the blood. Never- 
theless, snake bites may be poisonous for snakes of other species, 
and also for other members of the same species. Geoffroi 
and Hunauld, in 1737, and Fontana, in 1781, noted the anticoagu- 
lant action of venom, but the work of Weir Mitchell in 1860, 
and of Weir Mitchell and E. T. Reichert in 1886, served as the great- 
est stimulus to modern investigation. Mitchell and Reichert 
showed that the venom of the rattlesnake produces rapid coagula- 
tion of the blood and death, but that if the animal survives the blood 
is reduced in coagulability. C. J. Martin confirmed this in regard to 
Australian snakes and showed that the phenomenon could be con- 
trolled by dosage of the venom. In addition to hemolysis and 
alteration of coagulation, other properties are present, and Flexner 
and Noguchi showed in venom the presence of hemotoxins, in- 
cluding hemolysins and hemagglutinins, leucocytolysins, and an 
endotheliotoxin which they named hemorrhagin. Pearce showed 
that hemorrhagin produced lysis of endothelium leading to hemor- 
rhage. In addition, venoms contain proteolytic enzymes, invertase, 
lipase, and probably certain ferments dealing with coagulation. 
Martin found fibrin ferments which probably aid in thrombus for- 
mation. Lamb found that even citrated blood could be clotted by 
venoms. Negrete found the anti-coagulating element closely asso- 
ciated with the proteins of the venom. Morowitz claims the pres- 
ence of an antithrombokinase. Modern studies by Houssay 
Sordelli and Negrete with the venoms of fourteen snakes, Indian, 
American, and Australian, show that clotting time does not parallel 
closely the dose of venom, that venoms clot whole blood, plasma, 
and fibrinogen solutions, and that mammalian blood is more sus- 
ceptible than that of birds, batrachians, and snakes. The addition 
of citrate, oxalate, magnesium sulphate, hirudin, and peptone delay 
the action of the venom, the oxalate acting the most intensely. It 
seems likely that large doses of venom bring to bear a sufficient 
amount of fibrin ferment to produce clotting and that the later 
effects are due to the anti-coagulating power of the venom after the 
fibrin ferment is exhausted. Inasmuch as the hemolysis of venom 
is somewhat closely related in mechanism to hemolysis in general, 
it will be discussed in the chapter on Hemolysis (see page 141). 
Venom toxins resemble other toxins in that they are precipitated 
with proteoses, whilst the factor which produces local irritation 
comes down with globulin, although Faust maintains that the active 
principles of venoms are glucosides. Venom toxins are destroyed 
by heat, the cobra poisons as a class by 100 C., and the viper 
poisons by 85 C. They do not dialyze and deteriorate under the 


influence of light, radium, and oxiding agents. There is an incuba- 
tion period and the venoms are definitely and specifically antigenic. 

Venoms act in extremely small amounts. The fatal dose of 
cobra venom for man is probably o.oi to 0.03 gm., rattlesnake venom 
0.15 to 0.3 gm., and poisonous sea snakes o.ooi to 0.003 S-' or ten 
times as toxic as cobra venom. The bite of the cobras produces 
little pain and local reaction, probably due to its small content (2 
per cent.) of globulin, which contains the local irritant property of 
the venom. A feeling of stiffness spreads from the region of the 
wound, followed by vertigo and weakness of muscles of locomotion, 
tongue, jaw, esophagus, and preservation of senses, resembling a 
very acute bulbar palsy with death in a few hours. Gushing, how- 
ever, finds that the action of the poison is particularly upon motor 
nerve termini. The venom of the vipers produces a marked local reac- 
tion, probably due to its large (25 per cent.) globulin content, with 
pain, swelling, local bleeding, blood in the serous membranes and 
hematuria. Nausea and vomiting, excited reflexes, and even con- 
vulsions are followed by prostration, paraplegia of lower extremities 
which extends upward and resembles an acute ascending spinal 
paralysis with death in one to three days. Langmann states that, 
" if the patient recovers from the paralysis, a septic fever may de- 
velop; not rarely there remain suppurating gangrenous wounds 
which heal poorly." The suppuration of snake bites (viperidse) 
has been the subject of considerable study; Welch and Ewing 
ascribed this to loss of bactericidal property of the blood after venom 
poisoning. Flexner and Noguchi demonstrated a loss of the com- 
plement of the blood, an element necessary to its full bactericidal 
power. They believed that the complement was used up by the 
venom whose amboceptors require complement for their action, 
therefore leaving little or none free for the bactericidal amboceptors. 
Morgenroth and Kaya claim that the complement is actually de- 
stroyed by the venom. Of considerable importance in favoring infec- 
tions must be the local necrosis of tissue caused by the venom and the 
associated hemorrhage, aided by the customary radical surgery of 
the wound. 

The production of antisera was placed on a practical basis by 
Calmette in 1894 and Frazer in 1895. Calmette attenuated cobra 
venom for the first four injections by the addition of equal volumes 
of i per cent, gold chloride solution, and then gave small doses of 
the native toxin, gradually increasing until a powerful antivenin 
was developed. Phisalix and Bertrand attenuate viper venom by 
heating the first dose to 75 C. and then after two days giving one- 
half the minimum lethal dose of toxin. It was at first thought that 
the antivenin produced by cobra venom would protect against all 
venoms, but it was soon shown that the sera were specific for the 
venom employed. Antivenin also neutralizes that element of venom 
which induces loss of bactericidal power of the blood. Noguchi has 
shown that the antivenin of rattlesnake venom neutralizes the 


hemorrhagin. Such sera also contain precipitins for the proteins of 
the special venoms employed and for the serum proteins of the 
same species of snake. These are highly but not absolutely specific. 
The mechanism of venom-antivenin union is probably very closely 
similar to that of toxin-antitoxin unions of other varieties, although 
Kyes holds that the former is distinctly in the nature of the chemi- 
cal reaction between a strong acid and a strong base. 

Scorpion poison is secreted by special glands in the abdomen. In 
human adults the symptoms are rarely severe, except for marked 
local reaction, but it is stated that the bite of an African scorpion 
may kill children. As a rule, the most serious effects are from the 
subsequent infection of the wounds. Todd was able to prepare a 
specific immune serum for the poison of scorpions. According to 
Houssay, scorpion venom acts pharmacologically much as veratrin ; 
it is a smooth muscle stimulant. He states that serum therapy is 
useful and specific. 

Spider poison is secreted by glands in the thorax. The common 
spiders are not venomous, except the " cross spider " whose venom, 
much weaker in the saliva than in the ovaries, closely resembles 
snake venoms in chemical properties and agglutinin, and probably 
contains a neurotoxin. Sachs prepared an antivenin against this 
venom. Some of the larger spiders are extremely poisonous, par- 
ticularly the Malmigatte of southern Russia and related species in 
South America and Africa. Large numbers of cattle have been 
poisoned with as high as 12 per cent, mortality, but the bite is 
rarely fatal for man. 

The tarantula produces a poison which operates almost entirely 
locally, and it is stated that an antitoxin can be produced against the 
Russian tarantula. 

Centipedes. Certain centipedes secrete a poison in special glands 
that discharge through the claws, capable of producing considerable 
local reaction. But one case of fatal poisoning has been reported 
from Texas, that of a child four years old. 

Bees, wasps, and hornets secrete a poison closely similar for all 
three. Bee poison contains formic acid and in addition a poison 
which does not give the usual protein reactions, but is destroyed 
by proteolytic enzymes ; it resists heat to 100 C., weak acids, and 
alkalies. The poison contains a hemolysin which operates in much 
the same manner as does cobra hemolysin. The bite produces 
marked local reaction, but only in cases of extreme hypersuscep- 
tibility are there general effects or death. Part of the lack of 
severity of bee poison is due to the small dose injected, for if col- 
lected in large amounts and injected intravenously into dogs it can 
produce death. The resistance of professional bee keepers to the 
bites is probably due to the fact that repeated bites lead to de- 
velopment of immunity, although it is possible that the doctrine of 
the survival of the fittest may play its part. Ants probably pro- 


duce a somewhat similar poison in addition to formic acid. The 
" black flies " of the woods produce a poison not as yet identified, 
but no poison has as yet been isolated from the mosquito. Numer- 
ous other insects appear to have poisonous secretions, but as yet no 
studies have been made in detail as to their isolation and identification. 

Toads, frogs, and salamanders produce dermal secretions which 
are poisonous, several of which operate like digitalis and some like 
epinephrin. These poisons are interesting from a pharmacological 
point of view, but as they are not capable of producing immune re- 
actions in animals they deserve no extensive discussion here. 

Poisonous fish comprise several groups. One group secrete 
poisons in special glands, the poison being discharged through 
spines. Such poisons contain a hemolysin which requires an 
activator, as in the case of cobra-venom hemolysins. These poisons 
act as powerful local irritants and as cardiac depressants and may 
cause death. Only one variety of fish produces poisoning by its 
bite, the poison being secreted in the gums. Other fish are poison- 
ous when eaten even when quite fresh, the poison being found 
especially in the ova and ovaries. The symptoms may be of a 
severe choleriform type frequently fatal, or of a less severe gastro- 
intestinal type, not commonly leading to death. Certain fish, par- 
ticularly in the tropics, rapidly decompose with the formation of 
poisonous products or ptomains. The bites of crabs may produce 
peculiar erysipelas-like lesions or " erysipeloid," but the origin and 
nature of the poison are not known. Many individuals develop 
toxic symptoms after eating shell-fish and other sea food, in some 
cases due to the decomposition of the food, but in most instances 
due to a peculiar hypersusceptibility which will be discussed under 
Hypersusceptibility (see page 230). 

Eel serum deserves special consideration because of the fact that 
immune bodies can be produced. It is not poisonous when ingested, 
but is highly so if given intravenously and it produces conjunctivitis 
when instilled into the sac. Relatively large doses lead to rapid 
death -and small doses may produce cachexia and death after sev- 
eral days. The toxic 'element is in the albumin fraction of the 
serum and is destroyed by 58 C. for fifteen minutes. It contains 
a hemolysin and probably also a neurotoxin. The hemolysin does 
not act as an amboceptor, reactivation by fresh serum being im- 
possible after the eel serum has been heated. Immune sera can be 
produced which neutralize the hemolysin in vitro and also protect 
animals from death by the eel serum. The serum of lampreys and 
rays is similarly toxic. 

The parasitic protozoa and other animal parasites are strikingly 
free from substances which induce immunity. The protozoa show 
few exceptions to this rule. Cytolysins can be produced experi- 
mentally for amebse, but no such reaction takes place in human 
patients. Active immunity to trypanosome infection can be pro- 


duced, and it is claimed that immunity can be conferred passively. 
The trypanosomes, however, can become immune to trypanocides. 
Malarial parasites produce among other things a hemolysin, but 
there is no indisputable evidence that immunity occurs in malaria, 
nor have immune reactions been developed. Sarcosporidia of sheep 
produce a toxin fatal for rabbits in doses of o.oooi gm., against which 
an antitoxin may be produced in rabbits. Complement-fixation re- 
action is positive in infested sheep. Man may be infested by the 
cyst of one tape worm, the tenia echinococcus, the cyst contents 
being definitely toxic, as shown when a cyst ruptures into a body 
cavity, e.g., the peritoneum. Serum of infested patients contains a 
precipitin for the cyst proteins and also a complement-fixing body, 
Zapelloni reporting 93 per cent, positive complement-fixations in 500 
cases examined. Of the adult tape worms which infest man the 
dibothriocephalus latus is the most important from the immunologi- 
cal standpoint, although this parasite is rare in America. The 
proglottids contain a thermostabile hemolytic lipoid liberated oh 
the death of the segments by auto-digestion. There is also a ther- 
molabile hemagglutinin. It is probable that the hemolysin is 
either associated with other cytolysins or that a species cytolysin is 
present which also acts as a hemolysin. This is responsible for the 
primary type of anemia seen in dibothriocephalus latus patients. 
The serum of these patients contains a precipitin for the fluid ob- 
tained by antolytic digestion of the segments. Of the nematodes 
the ascaris, the trichinella spiralis, the hook worm, and certain forms 
of filaria have been investigated. Certain ascarids produce poison- 
ous substances without immunological relations. In regard to 
trichinosis Salzer has found that the serum of recovered patients 
has distinct therapeutic value in infested patients and protects ani- 
mals against experimental infestation. Complement-fixation has 
been found to be of value in the diagnosis of trichinosis. It has been 
claimed that the anemia of hook-worm infestation is due to a 
hemolytic poison, but there is doubt that this is as important as 
the small repeated hemorrhages produced by the bite of these para- 
sites. There is little of immunological significance in the studies of 
the filarise. The guinea-worm (filaria medinensis) contains in its 
body a violent irritant which may be discharged by rupture of the 
worm during forcible attempts at its removal, and leads to severe 
local inflammation and even to gangrene. 

Mammalia do not produce poisons except in the somewhat ques- 
tionable case of the male duck-bill platypus of Australia, a survivor 
of the very earliest forms of mammalian life. Special glands are 
said to secrete a poison like that of Australian snakes, which is dis- 
charged through a hollow movable spur on the hind foot. There is 
serious question as to the toxic properties of this secretion, certain 
authorities believing that the sequences of such wounds are due to 
infection and that the secretion is of importance only as a secondary 
sex character. The serum of certain mammals is toxic on injection, 


as, for example, beef serum, which in doses of 0.5 c.c. will kill a 
guinea-pig in a few minutes. Dog serum is also toxic for guinea- 
pigs in somewhat larger doses (i.o to 2.0 c.c.). Horse serum is toxic 
for cats in doses of i.o c.c. per kilo, and for guinea-pigs in doses of 
20.0 c.c. per kilo., but man is practically insusceptible, except in 
those cases of hypersusceptibility in which small doses of serum 
produce serious symptoms and even death. Such toxic sera con- 
tain hemolysins and agglutinins in small amounts and reduce the 
coagulability of the blood, but death is probably due to other factors. 
Except for cases of natural or artificial hypersusceptibility, the toxic 
element is destroyed by heat of 56 C. and is removed by 
animal charcoal. 





















General Introduction. -If a clear albuminous urine be boiled the 
invisible protein aggregates clump together, become visible as 
flocculi, and sink to the bottom of the test-tube. If to a colloidal 
suspension of mastic be added a proper concentration of common salt 
a similar flocculation of the mastic occurs. Red blood-corpuscles or 
bacteria shaken in physiologic salt solution form a cloudy suspen- 
sion of particles invisible to the naked eye. They may be clumped 
together by a variety of methods in similar flocculi which become 



clearly visible as small particles and sink to the bottom of the tube 
more quickly than would the individual cells in the original suspen- 
sion. The first example is one of precipitation and the last of 
agglutination. In the immunological sense, precipitation implies 
flocculation of a protein solution by means of specific antibodies, so 
that large aggregates are formed and thrown out of solution. Simi- 
larly the term agglutination signifies clumping together by means 
of specific antisera of cells originally in smooth emulsion, so that 
the clumps are visible microscopically or grossly, and sink rapidly 
to the bottom of the containing vessel. Animals may be immunized 
to a protein in solution, as, for example, blood serum or egg white, 
so that the animal's serum contains a body, the precipitin, capable 
of precipitating the protein used for immunization. Similarly bac- 
teria, red blood-corpuscles, or even other cells may be injected re- 

FlG. 3. Wooden box for holding rabbits during injections into or bleeding from the ear vein. 

peatedly into animals leading to the formation within the animal of 
a body, the agglutinin, appearing in the blood serum and capable of 
clumping the type of cell injected. These phenomena, although 
closely related and probably fundamentally identical in nature, will, 
for eminently practical reasons, be discussed separately. 


Bacterial Agglutination. Although others had observed the 
phenomenon of agglutination, Gruber and Durham, in 1896, were 
the first to study it intensively in the course of work on the colon 
bacillus and the cholera vibrio. They pointed out the specificity of 
the reaction and the fact that it differed in certain essentials from 
previously studied serum reactions. These points will be discussed 



in some detail, but it must be pointed out at once that the specificity 
is not absolute. It was soon found that blood-cells and later other 
body cells could be agglutinated by specific sera. It was also 
found that agglutinins of various kinds exist normally in certain 
sera, these being called normal agglutinins as opposed to the arti- 
ficially produced or immune agglutinins. It was found that the 
agglutinins resist heat of 56 C, a degree sufficient to destroy com- 
plement, and that after being rendered inactive by heat cannot be 
reactivated by fresh normal serum. It was soon observed that in 
the course of infectious disease due to a specific organism agglu- 
tinins are likely to develop, and this led to the discovery in Widal's 

FIG. 4. Method of obtaining blood from the posterior auricular vein of the rabbit's ear. The 

vein has been incised by means of a small hypodermic needle. The same position of the animal 

serves for intravenous injections which are given into the posterior auricular vein. 

clinic in Paris, a few months after Gruber and Durham's publica- 
tion, of the now widely used Widal reaction for typhoid fever. Con- 
versely with a serum of known type, the antigenic bacteria may be 
identified. The demonstration of agglutination may be by the 
microscopic method or by the macroscopic method. In our pre- 
sentation of the subject it is considered desirable to illustrate the 
points by actual experiment, and for this reason we proceed to take 
up the method of producing immune agglutinins in the laboratory 
and subsequently present the factors which qualify and modify 
the process of agglutination. 

Production of Immune Agglutinins. Injections for producing 
agglutinins may be subcutaneous, intraperitoneal, intravenous, or a 



combination of these, using first the subcutaneous or intraperitoneal 
routes followed later by intravenous injections. Bacteria are usu- 
ally killed by heat or chemicals before injection, although after im- 
munization is well under way living organisms may be employed. 
The use of living organisms is often of service in the development 
of a serum of high titer. 


FlG. 5. Method of complete bleeding from the femoral vessels of the rabbit (see 
text page 83). 

The following will serve as a fairly typical example of the process of 
immunization for the production of an anti-typhoid agglutinin. The cultures 
used are twenty-four hour agar slants inoculated by zig-zagging the loop 
back and forth over the surface so as to have the surface well covered by 
growth. A measured amount, 5.0 c.c. or 10.0 c.c. of sterile salt solution is 
added, the tube allowed to stand ten or fifteen minutes and then vigorously 
rotated between the palms of the hands. This procedure gives a much 
smoother emulsion than washing off by sucking in and blowing out from a 
pipette or by scraping off with a platinum loop and is less susceptible to 



contamination. The suspension is pipetted into a sterile tube and the growth 
killed by placing in a water bath of not less than 56 C. or more than 60 C. 
for two hours. Rabbits are desirable animals because of the ease of intra- 
venous injection. For ease in handling, the animal is placed in a box as shown 
in Figs. 3 and 4. The ear is shaved along the course of the posterior auricular 
vein situated near the posterior margin of the ear on its upper surface, is cleansed 
with soap and water and sponged over with alcohol. Usually the alcohol makes the 
vein stand out prominently, but if it does not, the ear may be pinched near its root 
so as to distend the vein, or, if necessary, brushed over lightly with a sponge dipped 
in xylol. Xylol should be used very sparingly, because of the danger of an 
inflammation, which may make subsequent injections difficult. Bleeding from 
the puncture may be stopped by pinching the ear for a few moments at the 
site of injection. Usually one ear is used for injections and the other for 

PIG. 6. A flask placed upright after blood has clotted 

with oblique surface. The serum drains to the bottom 

of the flask and is easily withdrawn. 

test bleeding. The earlier injections or bleedings are near the tip of the ear, 
the later ones approaching the base. The following protocol illustrates 
an immunization: 

Day Killed typhoid emulsion 

i 0.05 agar slant * 

6 o.i agar slant 

ii 0.2 agar slant 

1 6 0.2 agar slant 

21 0.2 agar slant 

* If 10 c.c. saline had been added to 
the culture, 0.5 c.c. suspension would 
contain 0.05 agar slant. 

Preliminary Titration. One week after the last injection 0.5-1.0 c.c. blood 
is withdrawn from an ear vein and the serum separated and titrated for the 
agglutinin. (See Fig. 4.) If the titer is not satisfactory, the immunization 
may be continued with living bacilli as follows : 

Day Living typhoid emulsion 
I 0.05 agar slant 

4 o.i agar slant 

8 0.2 agar slant 


After 7-10 days a further titration is made, and if still unsatisfactory the 
animal is discarded. As a rule, three animals are employed, and from these 
at least one will produce an agglutinin which will titrate 1-5000 or higher. 
The titer may be maintained by subsequent injections at longer intervals, but 
it is usually found desirable to kill the animal by bleeding and to preserve the 
serum in ampoules in the refrigerator. 

Bleeding the Immune Rabbit. The rabbit may be " bled out " by strapping 
it on a flat board, lightly anesthetizing and plucking the hair from the groin 
on one side. The skin is scrubbed 
with soap and water and then 
alcohol, and a long incision made 
in the line of the groin groove. 
(See Fig. 5.) This goes through 
the fascias and exposes the femoral 
vessels. The neck of a sterile 
150 c.c. flask is placed over the 
vessels just below Poupart's liga- 
ment and the vessels cut with the 
knife, the blood being caught as 
it spurts. As the bleeding con- 
tinues the head end of the board 
is raised and the animal's body 
squeezed until the flow ceases. 
Before disposing of the body, 
death should be assured by a 
blow fracturing the cervical spine. 
The flask is placed in an oblique 
position until the blood is firmly 
clotted, then placed upright in 
the refrigerator. (See Fig. 6.) 
This leaves an oblique surface of 
clot from which the serum flows 
out in the bottom of the flask. 
The blood may also be obtained 
from the carotid artery, but this 
requires more careful dissection, 
longer anesthesia and may require 
the insertion of a cannula. Practi- 
cally it gives no better results 
either in quantity of blood with- 
drawn or sterility of the process. 
Usually 15-20 c.c. serum are 
obtained after twenty-four hours 
in the ice-chest, and only occasion- 
ally is it necessary to centrifuge in 
order to obtain a clear serum. The 
serum is withdrawn as shown in 
Fig. 7 and placed in small sterile 
ampoules of dark glass, sealed and 
kept in the refrigerator. 

Macroscopic Titration. Titra- 
tion is usually by the macroscopic 
method, but an alternative is the 
microscopic method. For the ti- 
tration by the macroscopic method 

FIG. 7. Method of drawing up measured volumes into 
a graduated pipette. The rubber tube enables the 
worker to observe the ascent of fluid in the pipette 

V.U.UV, > *,j i n^.wo.-upi.. HH.LIIUU ^,.1^ to observe the ascent ot fluid m the pipette 
it IS necessary to have the growth and the position of the tip of the pipette. Fluid is 
from two or three agar slants, withdrawn from flasks in the same fashion, 

adding about 10.0 c.c. sterile salt 

solution to each tube and making an emulsion as described for immunization. 
The suspension is placed in a flask and killed either by heat (56 C.-6o C. for 
two hours), or by phenol i.o per cent, or formalin (40 per cent.) i.o per cent. 
The killing of the organisms is not necessary, but is desirable because of the 
added safety and because such killed emulsions may be preserved in the refrigera- 
tor for several days or a few weeks. Broth cultures may be used, but the 
hydrogen ion concentration of the broth may add a small factor of error not 
present in the saline suspensions. 


Dreyer, who has given much attention to agglutination in the diagnosis 
of typhoid and paratyphoid fevers in individuals who have been vaccinated 
against these diseases, maintains that heat and chemicals other than formal- 
dehyde are inferior to the latter in killing and preserving the bacterial suspension. 
He has given great attention to standardization of the reaction, an important 
but not infallible precaution, where a patient, as in the army, is likely 
to be examined in different laboratories during the course of the disease. 
On this basis Dreyer has shown that saline emulsions from agar cultures are 
inferior to broth cultures. Scheimann maintains in addition that the broth 
cultures furnish a more permanent standard. Laboratories in which such 
standards are prepared determine the optimum density of the agglutinable 
cultures and also keep the emulsions until the early deterioration of agglu- 
tinability produced by the formalin has reached a stationary point, after 
which the standards remain practically unchanged for ten months and 
probably longer. 

The primary test is carried out in small test tubes, with each dilution 
one-half that of the preceding one. This simplifies making the dilutions, 
especially if only one serum is to be tested. A row of twelve tubes is placed 
in a rack and each tube receives 0.5 c.c. salt solution. To the first is added 
0.5 c.c. immune serum, the mixture blown in and out of the pipette three times 
and 0.5 c.c. transferred to the next tube, the processes repeated and 0.5 c.c. 
transferred to the next tube, and so until the last tube is reached. In order 
to preserve the constant volume in each tube, 0.5 c.c. is discarded from the 
last tube. Thus there are dilutions 1-2, 1-4, 1-16, 1-32, 1-64, 1-128, 1-256, 1-512, 
1-1024, 1-2048, 1-4096. To each tube is added 0.5 c.c. bacillus emulsion, thus 
doubling each of the dilutions, so that instead of ranging from 1-2 to 1-4096, 
they range from 1-4 to 1-8192. In the twelfth tube are placed 0.5 c.c. salt 
solution and 0.5 c.c. bacterial emulsion to serve as a control of the emulsion 
and prevent error due to spontaneous clumping of the organisms. The tubes 
are placed in a water bath at 37 C. for one hour and then in the refrigerator 
over night. The clumping is observed with the naked eye, the clumps being 
visible and settling more rapidly than the bacterial emulsion. Should 1-512 
of the final dilution show agglutination and 1-1024 fail to show it, the titer 
lies between these two, and it is advisable to set up a series of tubes 1-500, 
1-600, 1-800, 1-900, i-iooo, and repeat. The same, of course, is true of the 
weaker dilutions, although beyond i-iooo the scale is more easily placed in 
grades of 200 rather than 100. The preparation of such dilutions is illustrated 
as follows: 

1 0.5 c.c. serum + 4.5 c.c. saline = i-io dilution 

2 0.5 c.c. No. i + 12.0 c.c. saline = 1-25 dilution 

3 0.5 c.c. No. i + 4.5 c.c. saline = i-ioo dilution 

4 0.5 c.c. No. 2 + 4.5 c.c. saline = 1-200 dilution 

5 0.5 c.c. No. 3 + i.o c.c. saline =1-300 dilution 

6 0.5 c.c. No. 2 + 5.5 c.c. saline =1-350 dilution 

7 0.5 c.c. No. 3 + 1.5 c.c. saline = 1-400 dilution 

8 0.5 c.c. No. 2 + 8.5 c.c. saline = 1-450 dilution 

9 0.5 c.c. No. 4 + 8.5 c.c. saline = 1-500 dilution 

Should we wish to determine a titer between 1-200 and 1-500, dilutions 
4-9 are placed, 0.5 e.c. in each of six tubes, 0.5 c.c. emulsion added to each, 
and in a seventh tube 0.5 c.c. saline and 0.5 c.c. emulsion as a control. The 
tubes are placed in the water bath and incubated as before. Similar protocols 
may be made if higher dilutions are required for the final test. Some workers 
prefer to set up primary dilutions of i-io, 1-50, i-ioo, 1-200, 1-500, i-iooo, 
1-2000, 1-4000, but this has no particular advantages as compared with the 
primary titration outlined above. 

Microscopic Titration. The microscopic method may be employed with 
the same method of dilution and mixing, simply removing a drop for obser- 
vation in a hanging drop preparation at the end of the period of incubation 
and examining with a 4-mm. lens. Another somewhat less accurate method is 
to place one loopful of each dilution on a coverslip and mix with a loopful of 
bacterial suspension, inverting the slip on a hollow ground slide, sealing with 
vaseline, incubating and reading the result. A still less accurate method is 
to place on coverslips or slides a row of loopfuls of salt solution, adding a 
loopful of serum to the first drop, mixing, transferring a loopful to the second 

FIG. 10. Microscopic drawing showing the agglutina- 
tion of a suspension of bacillus typhosus by blood serum 
from a human case of typhoid fever, as seen in the 
Widal test. 


drop and so on until the series of dilutions has been made, discarding a loop- 
ful of the last mixture and leaving one loopful of salt solution as a control, 
then adding to each drop a loopful of bacterial suspension. The slips or 
slides are inverted, sealed, incubated and read. In using slides, the trouble 
of sealing may be avoided by incubating in a moist chamber. The micro- 
scopic method is usually employed in the Widal test, the dilutions of patients' 
blood or serum being made by the same drop method, 1-20, 1-40, 1-80. Some- 
times a drop of dried blood is used, this being laked and dissolved by a drop 
of water and then made up to the first dilution of 1-20 by the addition of 
nineteen drops of saline. Frequently twenty-four-hour broth cultures of the 

FlG. 8. The Wright tube for obtaining small 
quantities of blood serum. 

FIG. p. Coiled pipette for taking up small quantities of fluids. Bubbling in the 
coil gives warning of the filling and prevents suction into the mouth. The tube may 
be made straight and plugged with cotton. Either may be used for withdrawing 
serum from the Wright pipette. Suction may be applied by the mouth directly or 
with a rubber tube or by means of a small nipple. 

typhoid bacillus are employed as the emulsion. Clearer results, however, are 
obtained by collecting blood in Wright tubes (Fig. 8) and allowing the 
serum to separate for dilution, and then employing a salt solution suspension 
of a twenty-four-hour agar slant culture. 

Specificity of Agglutinins Group Reactions. /The specificity 
of the reaction may be shown by setting up dilutions of the anti- 
typhoid serum obtained from the immunized rabbit against suspen- 
sions of bacillus typhosus, bacillus paratyphosus (A or B), and 
bacillus coli communis. An illustrative protocol follows : 

Typhoid immune serum 

B. typhosus 

B. paratyphosus A. 

B. Coli 











+ 1 ] 

'; - 




Salt solution 


This protocol illustrates two points, first, that the serum agglu- 
tinates its homologous bacteria in high dilutions, and second, that 
in strong concentrations it also agglutinates other organisms of the 
same group. Thus the specificity is not absolute throughout, but 
there is a " zone of absolute specificity," in this case between the 


dilutions oi 1-128 to 1-4096. The fact that the other two organisms 
are agglutinated is due to the phenomenon of " group reactions." 
In the same way, if an animal were immunized to bacillus coli the 
serum would agglutinate coli in high dilutions and typhosus in 
lower dilutions. The principle is also well shown in a table taken 
from Citron : 

Typhoid Cholera 

Agglutination of immune immune 

serum serum 

Against B. typhosus ....,,,,.,, 1-2,000 i-io 

Against B. paratyphosus i-ioo i-io 

Against B. coli 1-25 i-io 

Against V. cholerae i-io 1-3,000 

Absorption of Agglutinins. If specific sera for paratyphosus and 
coli were interposed in the above diagram it would be seen that these 
sera would clump the homologous bacteria in high dilution, and the 
others of the group in only low dilutions. This indicates that in 
each serum we may assume there are several agglutinins, one for 
the homologous organism, a major agglutinin or main agglutinin, 
and one for each of the other organisms of the group, minor agglu- 
tinins or partial agglutinins. This statement may be accepted for 
the present, although the conception will be somewhat altered in the 
theoretical discussion. Castellani has shown that if the major 
agglutinin is absorbed by its homologous organism the minor agglu- 
tinins disappear also, but that if one or several of the minor agglu- 
tinins be absorbed by other members of the group of organisms the 
major agglutinin remains. In order to make this clear we shall first 
illustrate the process of absorption and then apply it to the group 
reaction. It is well known that an animal may be simultaneously 
immunized to two or more types of organisms ; for example, bacillus 
typhosus and bacillus coli. The resulting serum may agglutinate 
typhosus in dilution of 1-4000 and coli in dilution of i-iooo. The 
absorption of the agglutinins may be shown as follows : 

Prepare thick suspensions of bacillus typhosus and of bacillus coli com- 
munis by suspending the twenty-four-hour surface growth of three slant agar 
cultures in about 5 c.c. saline. This is done by placing 5 c.c. in the first tube, 
making the suspension, then transferring to the second tube, suspending that 
culture and repeating in the third tube. The typhoid emulsion is killed by 
heat of 56 C. for one hour and the colon by heat at 60 C. for one hour. 
Add to 1.5 c.c. serum an equal volume of thick suspension of dead bacillus 
typhosus and in another tube place 1.5 c.c. serum with an equal volume of 
thick suspension of dead colon bacilli. The tubes are marked A and B. After 
mixing the emulsion of bacilli and serum the tubes are incubated at 37 C. 
and placed in the ice-chest for twelve hours. The tubes are centrifuged and 
the supernatant fluid pipetted off. The bacteria are resuspended and the sus- 
pensions diluted with salt solution about 1-20 or more, in order that agglu- 
tination may be easily observed. The supernatant fluid represents a 1-2 
dilution of the original serum. Place 0.5 c.c. each into test tubes and add 4.5 c.c. 
saline, making a dilution of 1-20, well under the titer of the serum. Of the 
diluted fluid A which has been absorbed by typhosus place 0.5 c.c. in a series 
of two tubes and add 0.5 c.c. thin emulsion of colon. After incubation the first 
tube will show no agglutination, and the second tube containing colon, whose 
agglutinin has not been absorbed, will show agglutination. Conversely place 
0.5 c.c. diluted fluid B in a series of two tubes, and add in order 0.5 c.c. thin 


emulsion of typhosus and 0.5 c.c. thin emulsion colon. After incubation only 
tube i shows agglutination, because the colon agglutinins have been ab- 
sorbed. The protocol of this experiment with the controls follows: 


1. Fluid A 0.5 c.c. -j- 0.5 c.c. typhosus = no agglutination. 

2. Fluid A 0.5 c.c. T 0.5 c.c. colon = agglutination. 


3. Fluid B 0.5 c.c. + 0.5 c.c. typhosus = agglutination. 

4. Fluid B 0.5 c.c. + 0.5 c.c. colon = no agglutination. 


5. Saline 0.5 c.c. + 0.5 c.c. typhosus = no agglutination. 

6. Saline 0.5 c.c. + 0.5 c.c. color no agglutination. 

This experiment shows only the essentials of the specific absorption. It 
may be further elaborated by making a series of dilutions of the treated 
serum so as to show the fact that the titer is essentially unimpaired. 



Fluid A 0.5 c.c. 

Typhosus emulsion 



0.5 c.c. 



0.5 c.c. 



0.5 c.c. 



0.5 c.c. 



0.5 c.c. 



0.5 c.c. 



0.5 c.c. 



0.5 c.c. 



0.5 c.c. 



0.5 c.c. 



Colon emulsion 



0.5 c.c. 



0.5 c.c. 



0.5 c.c. 



0.5 c.c. 



Typhosus 0.5 c.c. 

At the same 

time set up tubes 

as follows: 


Fluid B 0.5 c.c. 

Colon emulsion 



0.5 c.c. 



0.5 c.c. 



0.5 c.c. 



0.5 c.c. 



0.5 c.c. 



0.5 c.c. 



0.5 c.c. 



0.5 c.c. 



Typhosus emulsion 



0.5 c.c. 



0.5 c.c. 



0.5 c.c. 


Saline 0.5 c.c. 

0.5 c.c. 


Saline 0.5 c.c. 

Colon emulsion 0.5 c.c. 


This experiment shows that the process of absorption removes 
only the specific agglutinin and leaves the other agglutinin un- 
changed. As a matter of practical fact, the typhoid agglutinin re- 
mains unchanged, but the colon agglutinin may be somewhat reduced 
in titer, perhaps to 1-800 or even as low as 1-300. In a combined 
serum of this sort with the typhoid agglutinin of high titer, part of 
the agglutinin for colon is the result of a typhoid minor agglutinin 
which is removed by absorption with typhosus, thus reducing the 



colon titer. The primary colon titer of 1000 would have a very low 
content of minor agglutinin for typhosus, the removal of which 
would leave the primary titer for typhosus practically unchanged 
after absorption with colon bacilli. 

The differences of absorption of major and minor agglutinins may be 
illustrated by the use of a typhosus immune serum. We may use, for illustra- 
tion, as closely related organisms bacillus typhosus and bacillus paratyphosus B. 
Preliminary titration of the serum is carried out as usual against bacillus 
typhosus and bacillus paratyphosus B. Let us suppose that the serum shows 
a titer of 1-4096 for typhosus and 1-512 for paratyphosus B. Thick emulsions 
of typhosus and para B are made as described in the previous experiment, 
killed by 56 C. for one hour and mixed in equal volume with 1.5 c.c. serum, 
incubated for one hour and refrigerated for twelve hours, then centrifuged 
and the fluid pipetted off. The experiment with the results may be illus- 
trated in the following protocol: 



















Fluid A 0.5 c.c. 
by typhosus) 

Typhosus emulsion 


0.5 c.c. 


0.5 c.c. 
0.5 c.c. 
0.5 c.c. 
0.5 c.c. 


0.5 c.c. 


0.5 c.c. 
0.5 c.c. 

Fluid A 0.5 c.c. 
(absorbed by 

Para B emulsion 



Saline 0.5 c.c. 
Saline 0.5 c.c. 

Typhosus 0.5 c.c. 
Para B. 0.5 c.c. 

Fluid B 0.5 c.c. 
(absorbed by 
Para B) 

Typhosus emulsion 


0.5 c.c. 

-2 5 6 

0.5 c.c. 
0.5 c.c. 
0.5 c.c. 
0.5 c.c. 


0.5 c.c. 


0.5 c.c. 
0.5 c.c. 
0.5 c.c. 

Para B emulsion 


0.5 c.c. 

Saline 0.5 c.c. 
Saline 0.5 c.c. 

0.5 c.c. 
0.5 c.c. 
0.5 c.c. 
0.5 c.c. 
0.5 c.c. 
Typhosus 0.5 c.c. 

Untreated serum 


Typhosus 0.5 c.c. 
Para B. 0.5 c.c. 





It will be seen from these protocols that absorption by the major agglu- 
tinogen, bacillus typhosus, removes both the major and minor agglutinins, 
and that absorption by the minor agglutinogen removes only the minor agglu- 
tinin, although it is true that even though the titer of the major agglutinin is 
not reduced it may agglutinate in smaller clumps. 

Inhibition Zones. It is sometimes found that in powerful agglu- 
tinins there is an " inhibition zone " in the more concentrated dilu- 
tions. Thus a serum may agglutinate as follows : 

Tube Serum dilution Result 

1 I-IO 

2 I-IOO + 

3 1-1,000 +++ 

4 1-2,000 -| | \- 

5 1-4,000 ++ 

6 1-6,000 -f- 

7 1-8,000 

This phenomenon is somewhat more frequently observed in sera 
that have been preserved for a considerable time in the moist state. 
If a serum with a titer of i-iooo, which originally showed agglu- 
tination in all dilutions up to 1000, is preserved and after several 
months titrated again, it may fail to agglutinate in i-io, may 
agglutinate only weakly in i-ioo, and completely in 1-500. If the 
tube containing i-io dilution is centrifuged, the supernatant fluid 
drawn off, the bacteria again suspended and placed with the serum 
in dilution of 1-500, there is no agglutination. The same is true if 
these treated organisms are placed in contact with a fresh agglu- 
tinating serum. The same phenomenon is obtained if the serum 
first used is a fresh one of high titer with an inhibition zone, 
and the bacteria are removed from the low dilutions in which they 
have failed to agglutinate. The bacteria have become inagglutin- 
able by treatment with the serum in these concentrations. Simi- 
larly, heating an agglutinating serum to 65 to 70 C. destroys its 
agglutinating properties, but if it is added to bacteria they become 
inagglutinable when treated with fresh active serum. This phe- 
nomenon is strictly specific and operates only in the presence of the 
homologous organism. This peculiar character of agglutinins has 
been closely linked with the Ehrlich conception of immune bodies 
and is explained as due to the presence in sufficient concentration of 
" agglutinoids." The term agglutinoid is applied to that part of the 
agglutinin which has a specific binding affinity for the cell, but has 
been deprived of the thermolabile and more easily destructible frac- 
tion which has the power of producing clumping. This explanation 
will be discussed more in detail in the general discussion 
of agglutinins. 

The influence of heat on agglutination has been studied exten- 
sively. As has been indicated, heat will destroy agglutinins, but 
certain agglutinins are destroyed by degrees of heat which fail to 
destroy others. Most agglutinating sera are rendered inactive at 
60 to 65 C., but anti-plague agglutinin is destroyed at 56 C, 


whereas others do not disappear until 80 C. has been reached. 
Wells states that " purified typhoid agglutinin may resist 80 to 90 
degrees." Agglutinins cannot be reactivated by the addition of 
fresh serum, even though the temperature may have been adjusted 
so that the agglutinoid remains. 

A simple experiment for the demonstration of the influence of heat on 
agglutinins is as follows: The typhoid immune serum, the production of 
which has been described above, and also the killed typhoid suspension may 
be used. In each of three tubes place 0.5 c.c. serum diluted i-io, and into a 
fourth tube 0.5 c.c. salt solution. Tube i is heated in a water bath at 56 C. 
for one-half hour, tube 2 heated at 70 to 75 C. for one-half hour, and 
tubes 3 and 4 kept at room temperature. After cooling tubes I and 2, add 
0.5 c.c. bacterial emulsion to each tube and incubate for one hour at 37 C. 
Agglutination will not occur in tube 2, the serum having been heated to 70 to 
75 C., nor in the control tube with saline. The unheated serum and the 
serum heated to 56 C. will agglutinate powerfully. It will be found also that 
the addition of 0.1 c.c. fresh guinea-pig serum (complement) to tube 2, and 
subsequent incubation will fail to produce agglutination. 

It is of interest to note that the degree of concentration of serum 
has some influence on the degree of heat necessary for destruction. 
For example, Koeckert in this laboratory found that normal un- 
diluted iso-hemagglutinins are destroyed at 65 to 66 C. for 
thirty minutes, but that in high dilutions they are destroyed at 62 C. 
for thirty minutes. 

The influence of electrolytes on the phenomenon of agglutination 
is of considerable importance from the theoretical point of view 
because of the resemblance to flocculation of colloidal suspensions. 
Bordet, who discovered this fact, compared the reaction to the 
throwing down of the alluvial matter in rivers as the fresh water 
meets the salt water of the ocean. By previously dialyzing the salts 
out of the bacterial suspension and the specific serum he showed 
that agglutination would not occur, but that if the mixture was 
salted in proper concentration the reaction would take place. It is 
possible, however, to agglutinate bacteria by certain concentration 
of salts, particularly of the heavy metals, but such concentration is 
always much stronger than is necessary for salting, as described in 
the Bordet experiment. 

The demonstration of the influence of salts may be seen in the following 
experiment, taken from Zinsser, Hopkins and Ottenberg. For this experi- 
ment the killed typhoid suspension and the anti-typhoid serum as employed 
in previous experiments may be used. " Place in each of two centrifuge tubes 
with pointed tip 2.0 c.c. of the suspension. To tube A add 2.0 c.c. of agglu- 
tinating serum diluted 1-50. To tube B add 2.0 c.c. distilled water. Allow 
the tubes to stand at 37 C. for thirty minutes. Centrifugalize the tubes at 
high speed until the supernatant fluid is clear." Pipette off the fluid and "to 
the washed sediments add 2.0 c.c. distilled water and draw the mixture re- 
peatedly in and out of the capillary pipette in order to break up the clumps and 
obtain an even suspension. Set up the following tests in agglutination tubes : 

1 Sediment A 0.5 c.c Distilled water 0.5 c.c. 

2 Sediment A 0.5 c.c. 10 per cent NaCl 0.09 c.c. Distilled water 0.5 c.c. 

3 Sediment A 0.5 c.c. 0.8 per cent. CuSO 4 0.02 c.c. Distilled water 0.5 c.c. 

4 Sediment B 0.5 c.c. 0.8 per cent. CuSO 4 0.02 c.c. Distilled water 0.5 c.c. 

5 Sediment B 0.5 c.c. 0.8 per cent. CuSO 4 o.i c,c. Distilled water 0.5 c.c. 

6 Sediment B 0.5 c.c Distilled water 0.5 c.c. 


" The tubes are placed in the water bath at 37 C- for one hour and then 
observed. Tubes 2, 3 and 5 should show agglutination." In tube A the 
bacteria have been ' sensitized ' with the immune serum, and after the clumps 
have been broken up are ready again for clumping under proper conditions. 
In tube I the addition of distilled water does not provide the essential con- 
ditions, but in tubes 2 and 3 the addition of electrolytes favors the reaction. 
In tube B the bacteria have not been sensitized, but of the tubes 4, 5 and 6, 
the concentration of the copper sulphate is such as to induce clumping in 
itself, a phenomenon frequently seen in certain concentrations of salts of 
the heavy metals, such as zinc, lead and mercury. 

Influence of Hydrogen Ion Concentration. It has been shown 
by Michaelis and others that bacteria may be agglutinated by pro- 
viding a proper hydrogen ion concentration, and it was hoped that 
this might provide a means of rapid identification of organisms. 
Proteins, for example, have a specific and constant optimum con- 
centration of H ions for their precipitation. In the case of bacteria 
it was shown, for example, that bacillus typhosus was agglutinated 
by a hydrogen ion concentration of 4 to 8 X io~ 5 , whereas para- 
typhosus requires 16 to 32 X io~ 5 , colon bacilli not being agglutin- 
able by this method. It has been shown, however, that this 
differentiation is not so sharp as was at first supposed, that differ- 
ent strains show considerable irregularity, and that there is over- 
lapping of one species with another. A combination of serum and 
acid agglutination has shown that bacteria sensitized by serum can 
be more readily agglutinated than are non-sensitized bacteria. The 
specific characters of bacterial proteins are probably due to such a 
slight variation in the arrangement of the molecular structure that 
a satisfactory differentiation by changes in hydrogen ion concentra- 
tion is not at present feasible. Eisenberg has recently studied the 
problem with 584 races of bacteria, of which 537 were of the colon- 
typhoid group, and found no differential diagnosis possible with the 
acid agglutination method. He also found flocculation with salts 
of the heavy metals extremely variable. 

The Mechanism! of Agglutination. The data given in the pre- 
ceding paragraphs outline the most important phases of the phe- 
nomenon of agglutination, and any discussion of the mechanism of 
the process must be based on these fundamentals. The chemical 
nature of the agglutinogen is, of course, closely combined, if not 
identical, with the protein of the cells, but is in no sense dependent 
for its activity on the existence of life within the cell. Agglutinogens 
are not destroyed by mild concentrations of formalin, phenol, heat, 
or ultra-violet rays which are sufficient to destroy the life of the cell 
itself. They pass through dialyzing membranes more rapidly than 
do the agglutinins, and therefore are probably made up of smaller 
molecules. That they pass through collodion sacs can be shown by 
implanting such sacs, filled with killed typhoid organisms, in the 
peritoneal cavity of rabbits and observing the development of agglu- 
tinins in their blood ; an observation which has been confirmed by 
Reimann in this laboratory. Old broth cultures contain in the fluid 
agglutinogens which may neutralize agglutinins and which may 


serve also to produce agglutinins upon injection. Thus it would 
appear that agglutinogens are bodies of small molecular size capable 
of slow diffusion and almost certainly protein, although Stuber 
maintains that they are of fatty nature. The influence of heat on 
agglutinogens has been carefully studied by Joos, who concluded 
that the agglutinogen consists of relatively thermolabile and ther- 
mostable constituents (the dividing line being 60 to 62 C.) which 
induce the formation of separate agglutinins. The thermostable 
fraction resists heat up to 165 C., is soluble in alcohol, and does 
not give protein reactions, whilst the thermolabile fraction gives all 
the protein reactions. This work is more fully discussed subsequently. 

Alterations of Agglutinability. Of considerable interest in con- 
nection with agglutinogens is the alteration of agglutinability of the 
cell. This probably is more closely associated with the cell as such 
than with the agglutinogen. If bacteria are heated above 65 C. 
they are not agglutinable by specific immune sera, but can absorb 
agglutinin from the sera. Organisms freshly isolated from cases of 
infectious disease often show similar reductions of agglutinability, 
but recover it after prolonged growth on artificial media. This is 
likely to be true in the case of " carriers," and Welch has referred to 
it as a quasi-immunity which the bacteria themselves have acquired 
by acting against the immune bodies of the host, an immunity, how- 
ever, which the organisms lose on living in the environment of the 
artificial culture media. Such inagglutinability may be produced 
artificially by growing the bacteria on media containing a specific 
immune serum, heated to destroy any bacteriolytic influence. In a 
personal communication to us M. Cooper has stated that the pres- 
ence of capsules about bacteria serves to establish a quasi-immunity 
for the organisms against antibodies, and that such capsules appear 
after cultivation in immune sera. This peculiar phenomenon is ex- 
plained on the Ehrlich theory by assuming that the bacteria are 
practically exhausted of receptors. Nevertheless, such inagglu- 
tinable bacteria upon injection into animals lead to the production 
of agglutinins for agglutinable strains, but not for inagglutinable 
strains. It has also been assumed that they are saturated with 
agglutinoid, but in America, at least, the Welch theory has been 
given wide acceptance as an important philosophical conception. 
Not only may agglutinability be altered, but different strains of an 
organism show natural differences in agglutinability. For example, 
Cole has shown that against a specific agglutinating serum five 
strains of pneumococcus showed titers of 1-4000, 1-4500 (2), 1-7000, 
and 1-8000. These are not " types " of a species but strains, and show 
no specific agglutinability for sera produced by the strain in question. 

The Nature of Agglutinins. The chemical study of the agglu- 
tinins shows that, like antitoxins, they are precipitated out of the 
serum in the globulin fraction, and so far they have not been fur- 
ther purified. They pass through filters less readily than their 
antigens, and therefore have a larger molecular structure. Pepsin 


digestion destroys the agglutinins fairly readily, but trypsin acts 
more slowly. Alkalies even when dilute are destructive, but acids 
operate less actively. They are absorbed by charcoal. They are 
not thrown down in the precipitate formed by specific precipitating 
sera. The influence of heat on agglutinins has been the subject of 
much study. The work of Joos was conducted with both agglu- 
tinogen and agglutinin. As mentioned above, he demonstrated the 
presence in the bacterial antigen of a thermolabile A agglutinogen 
and a thermostable B agglutinogen, the dividing line being 60 to 
62 C. The injection of heated antigen (B agglutinogen) gives rise 
to the formation of B agglutinin, which in contrast to the antigen is 
destroyed by heat of 60 C., but reacts with both A and B agglu- 
tinogens. The injection of the unheated bacilli containing both A 
and B agglutinogen leads to formation of both agglutinins, but the 
B agglutinin can be removed by heat leaving the thermostable A 
agglutinin, which reacts only with the A agglutinogen. The essen- 
tials of this work have been confirmed, although Scheller working 
with bacillus typhosus found that the B agglutinin is reduced in titer 
but not completely destroyed at 60 to 62 C. Scheller showed 
further that the heated bacteria (B agglutinogen) absorb agglu- 
tinins from the sera more readily than do unheated bacteria, and that 
they give the highest titers with the serum. 

According to the Ehrlich scheme, agglutinins have a haptophore or 
combining group and a zymophore group which causes the agglutination. 
This zymophore is killed by heat and deteriorates on long standing to form 
the agglutinoid (or agglutinin free from zymophore), which has combin- 
ing but not agglutinating power. Thus in the side-chain theory the 
agglutinins (and precipitins) differ from the theoretical simplicity of 
the antitoxins and constitute the receptors of the second order. 

The Physical Basis of Agglutination. The mechanism of agglu- 
tination is such that the reaction takes place in constant proportions, 
thus likening it to a simple chemical reaction. The reaction is re- 
versible, however, in that simple shaking, the use of organic and 
inorganic acids and acid salts, as well as alkalies and heat of 70 to 
75 C., can break the clumps into cell units; but after this separa- 
tion fresh agglutinating serum cannot operate again. It has been 
shown further that agglutinins can be separated from bacteria- 
agglutinin combinations by the electric current ; therefore, the agglu- 
tinins are not destroyed by the union with the bacteria. Many of 
the older workers believed that the reaction occurred because of 
changes in the outer layers or ectoplasmic substance of the cells. 
Gruber at first maintained that a substance, glabrificin, was taken 
from the serum by the cells which made their outer surfaces sticky 
and caused adhesions when their motility brought the bacteria in 
contact with one another. Malvoz and others held that the reaction 
depended upon the entanglement of the flagella of the bacteria. 
Neither of these ideas is consistent with the fact that non-motile 


bacteria and other cells are subject to agglutination, but no definite 
proof is at hand to show that the ectoplasmic substance is not of 
considerable importance. The influence of salts on agglutination 
lends much support to the conception that agglutination is a col- 
loidal phenomenon. As has been indicated above, the presence of 
electrolytes is essential to the reaction, but salts, acids, and salts of heavy 
metals, if present in sufficient concentration, may of themselves produce 
agglutination. On the other hand, salts in strong concentration 
serve to prevent the action of agglutinin. When bacteria have ab- 
sorbed agglutinin, very small amounts of salt serve to bring about 
agglutination. If a suspension of bacteria and an agglutinating 
serum are each dialyzed free of salt and the two mixed, the bacteria 
absorb agglutinin. This is shown by the fact that the supernatant 
fluid after centrifugalization is free of agglutinin, but agglutination 
occurs on addition of salt. Bordet interpreted the phenomenon of 
agglutination as having two phases, first that of sensitization of the 
bacteria by the agglutinin, and second, that of agglutination of these 
agglutinin-bacteria by the salt. It may be stated in other terms 
that the bacteria are primarily suspensions of protected colloids 
which are so altered by the agglutinin that they become unprotected 
and precipitable by salts, or that they become more permeable for 
electrolytes. In fact, it has been shown that sensitized bacteria 
take up salts more readily than unsensitized. The similarity of 
bacteria to protected colloids is also borne out by Porges, who 
showed that while encapsulated organisms are inagglutinable, the 
solution of their capsules by heating in weak acid renders the bac- 
teria agglutinable. Bacteria carry electro-negative charges and move 
toward the anode, whereas agglutinins are electro-positive. The 
sensitized bacteria are agglutinated by the current between the poles, 
although the sensitized bacteria move slowly toward the anode. 
The small amount of salt necessary for agglutination further sup- 
ports the influence of electrical charge and thus furnishes further 
analogy with colloidal precipitation. Neisser and Friedemann have 
studied the similarities of agglutination and colloidal precipita- 
tion and offer much in support of such analogy. Two protocols 
may serve to show the importance of their work, one dealing 
with the so-called sensitization and the other with inhibition zones. 
Just as salt influences agglutinin and agglutinogen, so may it 
influence mastic and gelatin solutions, as may be seen in the follow- 
ing experiment : 

i.o c.c. mastic i.o c.c. mastic + o.ooor c.c. 

(i-io original emulsion) 2% gelatin sol. and 

10% NaCl Sol. diluted to 3.0 c.c. diluted to 3.0 c.c. 

I.O C.C. + + 

0.5 c.c. 

0.25 c.c. 

0.125 c.c. + 

0.05 c-c. 

0.025 c.c. 


Furthermore, they offer a protocol showing the similarity be- 
tween the reaction of colloidal iron hydroxide upon mastic emul- 
sions and the agglutination phenomenon in reference to inhibition 
zones. It will be seen that stronger concentrations of the iron 
hydroxide fail to precipitate, thus simulating the action of strong 
concentrations of an agglutinating serum of high titer or of an old 
serum. The protocol follows: 

Colloidal iron hydroxide Mastic emulsion 
1.0 I.O C.C. 

0.5 i.o c.c. 

0.25 i.o c.c. 

O.I I.O C.C. 

0.5 i.o c.c. 

O.02S 2.O C.C. 

O.OI I.O C.C. 

0.005 i.o c.c. 

0.0025 i.o c.c. 


This latter protocol is of significance not only in relation to 
agglutination, but is of importance also in connection with the 
Neisser-Wechsberg phenomenon of complement-deviation (not 
fixation) discussed in connection with bacteriolysis. As Zinsser says, 
" it seems to be a universal fact governing the union of colloidal 
substances, that definite quantitative proportions must be main- 
tained in order to lead to reaction, this being, possibly, explicable on 
the basis that actual union can take place only after disturbance of 
the electrical balance which keeps the particles apart." The assump- 
tion that agglutinoids have an important bearing on the presence of 
inhibition zones is not necessary if we accept the colloidal nature of 
agglutination. This does not entirely controvert the existence of 
altered agglutinin with a binding power for agglutinogen. 

Not only may salt-free bacteria-agglutinin combinations be 
agglutinated by salts but, as Friedberger has shown, certain organic 
substances, such as dextrose and asparagin, serve also to produce 
agglutination in such salt-free mixtures. These substances do not 
dissociate in solution as do salts, and therefore produce no electric 
phenomena. This fact presents a certain objection to the final 
acceptance of the colloidal theory of agglutination, but it is possible 
that the mechanism in this instance is of a nature different from 
that of the immunological process, and certainly the great mass of 
evidence is in favor of the reaction of agglutination being of 
colloidal nature. 

Nothing has been definitely brought forward in the physico- 
chemical examination of agglutination to explain specificity, except 
the fact previously indicated, that variations of hydrogen ion con- 
centration have a relatively specific action on bacteria. As is 
known, the definite identification of bacteria by this method has 
not been satisfactory. The specificity of immune serum agglutina- 

9 6 


FIG. ii. The nip- 
ple pipette for 
making mixtures 
of fluids and bac- 
terial suspension. 
The pencil mark is 
seen a short dis- 
tance above the 


tion is also a relative matter, as is shown in the group 
reactions, and if electric phenomena play a part in spe- 
cificity they are more delicate than can be demon- 
strated by present chemical or electrical methods. 
Bordet, who laid no emphasis on the electrical reac- 
tions, thought that the process of sensitization of bac- 
teria by agglutinins is in essence a denaturing of the 
bacterial proteins, and that the specificity of the process 
depends on the degree of denaturation. 

The Dreyer Test. The Widal test has been described 
(page 85). This test has been of the greatest service in 
the diagnosis of typhoid and paratyphoid fevers but the 
introduction of vaccination on a large scale has reduced the 
value of the test as a diagnostic sign of actual disease, be- 
cause vaccinated individuals give a positive test. Dreyer 
studied the course of agglutination in typhoid and paratyphoid 
fevers, and found that the .agglutinative titer of the blood 
follows, during the course of the disease, a fairly regular curve, 
increasing to the third week and then declining. Although 
the titer may be higher at the beginning of the disease in 
vaccinated individuals than in others, the titer follows the 
same general curve. Of more importance is the differentia- 
tion between typhoid and other infections in the vaccinated. 
This has been of the utmost importance in the World War 
in distinguishing between febrile disease, such as trench fever 
or malaria, and typhoid or paratyphoid. The test is made by 
the macroscopic method for agglutination, and must be re- 
peated at weekly intervals in order to determine the curve 
of agglutinins. Not infrequently the first test may show a 
titer so much higher than occurs after vaccination that a 
presumptive diagnosis is justifiable. Under war conditions 
the transfer of patients often made it necessary to perform 
the tests in several different laboratories, and to provide for 
this the Oxford Standards Laboratory prepared emul- 
sions of the bacilli for distribution. For this purpose 
the organisms were grown for twenty-four hours in pep- 
ton veal broth, then shaken well and o.i per cent, for- 
malin (40 per cent, formaldehyde) added. The culture was 
stored at 2 C. and shaken frequently during four or 
five days. At the end of this time it was usually sterile. 
It was then diluted to standard opacity by means of salt 
solution, to which was previously added o.i per cent, 
formalin. It was further standardized as to agglutina- 
bility and labeled with a factor so as to provide means 
whereby tests in different laboratories could be estimated 
on the same basis. 

The blood for the test can be obtained in a Wright 
tube, but it is preferably taken from the cubital vein 
into a centrifuge tube, so as to provide a fairly large 
amount of serum. In order to make the method appli- 
cable in laboratories where graduated pipettes are not 
available, Dreyer made all the dilutions with a nipple 
pipette of drawn-out glass tubing similar to that illus- 
trated in Fig. n, except that the drawn-out part is wider 
and shorter. Three rows of 7 x 75 mm. test tubes are then 
set up and further dilutions made according to the follow- 
ing scheme: 

.o drop 
5 drops 

8 drops 

9 drops 
10 drops 

Serum Bacterial suspension Dilution equals 

IO drops 
5 drops 
2 drops 
I drop 
o drop 

15 drops 
15 drops 
15 drops 
15 drops 
15 drops 








The three rows of tubes are set up so as to use suspensions in each row 
of bacillus typhosus, paratyphosus A, and paratyphosus B. The dilutions 
may be carried further if necessary. The tubes are incubated in a water bath 
at 55 C. for two hours, are read immediately, and, if desired, again after 
twenty-four hours in the refrigerator. The standard method of Dreyer may 
be adapted to other methods of dilution and incubation, but must be the 
same in the study of every case. 

In unvaccinated individuals agglutination in a dilution of 1-25 
against bacillus typhosus justifies suspicion, and if marked in dilu- 
tion of 1-50 is nearly always diagnostic. Browning offers the fol- 
lowing table as indicating positive reactions in each of the 
diseases indicated. 

B. typhosus 
B. paratyphosus A. 
B. paratyphosus B. 

Serum dilution 

1-50 (or even lower 1-20) 

These criteria are not applicable to vaccinated persons or those 
who have previously had typhoid or paratyphoid fever. Martin and 
Upjohn examined seventy-five persons from, seven to fourteen 
months after typhoid vaccination and found that the serum of two- 
thirds agglutinated bacillus typhosus in serum dilutions of 1-200, 
and that of one-tenth agglutinated in dilutions of 1-800. These are 
higher levels than are usually reached by unvaccinated persons dur- 
ing the course of the disease. Vaccination with typhoid vaccine 
produces minor agglutinins for para A and B, but in very low con- 
centration. Triple vaccines produce agglutinins for para A and B, 
but rarely in dilutions exceeding 1-50 or i-ioo. The following 
chart, taken from Mackie and Wiltshire, as quoted by Browning, 
illustrates the change in titer of blood serum in the course of infec- 
tion with bacillus paratyphosus A. 

Serum dilutions 

i 50 


I 2OO 

I 5OO 



Fourth or fifth day of illness: 
B. typhosus 

+ + + 

+ + + 
+ + + + 
+ + 



+ + + + 

+ + + + 



B. paratyphosus A 

B. paratyphosus B. 

Thirteenth day of illness: 
B. typhosus 

B. paratyphosus A 

B. paratyphosus B 

The first test in this patient was strongly suggestive, since it is 
rare in a vaccinated individual to find the titer for either para A or B 
to exceed that of typhosus. In our experience typhoid in the vac- 
cinated is likely to show titers in the first week of 1-500 for typhosus, 
i-ioo for para A, and 1-50 for para B ; toward the end of the 
second week they are likely to be, respectively, 1-2500, 1750, 
1-250; and in the third week 1-3000 or higher for typhosus with 
slight increases for para A and B. The titers then subside. It will 
be noted that infection increases not only the major but also the 
minor agglutinins. 


Space does not permit a complete discussion of the results of the 
test, but it may be said that a positive Dreyer test indicates the 
presence of some form of enteric fever. If, however, the isolation 
of organisms from the stools indicates the nature of the disease the 
test may sometimes mislead. For example, we have found para- 
typhosus B in the stools of a patient whose serum titer curve indi- 
cated the presence of a para A infection. The test should go hand 
in hand with careful clinical study and bacteriological examination 
of the blood, feces, and urine. 

Hemagglutinins. The agglutination of blood-cells and other 
body cells follows the same general principles laid down for bacterial 
agglutinins. In the case of agglutinins for red blood-corpuscles the 
name hemagglutinins has been adopted. These may be divided into 
auto-hemagglutinins., iso-hemagglutinins, and hetero-hemagglu- 
tinins. The auto-hemagglutinin is contained in the same blood as 
the cells it agglutinates, but certain factors operate to prevent agglu- 
tination in the living body. For example, Rous and Robertson have 
shown the presence in rabbits, which had received repeated small 
blood transfusions, of an auto-hemagglutinin which operates at 
temperatures lower than that of the animal, but on raising the tem- 
perature to 38 to 40 C. the clumps break up and a homogeneous emul- 
sion results. The same workers also demonstrated the presence of 
auto-agglutinins in rabbits subjected to repeated withdrawal of 
small quantities of blood. It has been stated that this phenomenon 
may also occur in acquired hemolytic jaundice (Hayem-Widal 
type), pernicious anemia, malaria, and other diseases, but more 
recent studies tend to contradict this statement. Hornby states 
that auto-hemagglutinins have been demonstrated frequently in 
animals infected with trypanosomes. Hetero-agglutinins were dis- 
covered by Creite and Landois, who noted that the serum of certain 
animals produced agglutination when brought in contact with the 
cells of certain other species; for example, the serum of the goat 
and the erythrocytes of rabbit, man, or pigeon. Bordet discovered 
in the course of his studies on hemolysins that if an animal is im- 
munized with the erythrocytes of another species, the blood serum 
will contain not only hemolysin, but also hemagglutinin for the 
cells used in immunization. Thus we have to consider normal 
hetero-hemagglutinins and immune hetero-hemagglutinins. Such 
normal antibodies are present in low titer, but immune agglutinins 
of this sort may be induced up to titers of several thousand. The 
methods employed for the production of such agglutinins are the 
same as those for producing hemolysis and will be considered under 
that subject. The determination of the titer of hemagglutinative 
sera is by essentially the same methods as for bacterial agglutinins, 
save that the cells are washed as for experiments in hemolysis, and 
usually a fixed percentage emulsion of cells is employed. The influ- 
ence of heat and other physical agents, as well as chemicals, is much 
the same as for hemolysins (see page 115). 


Iso-hemagglutinins, Classification. Iso-hemagglutinins are 
those which exist in certain members of a species for cells of cer- 
tain other members of the same species. Although iso-hemagglu- 
tinins may somewhat rarely occur in lower animals, they appear 
with great regularity in human blood. They were discovered in 
1906 by Landsteiner and Shattock, working independently. 
Landsteiner, by a study of the interaction of sera and corpuscles, 
classified all human bloods in three groups and determined that the 
property of iso-agglutinination is normal to man and does not vary 
under pathological conditions. Hektoen noted in 1907 that the three 
groups do not include all individuals, and in the same year Jansky 
published the classification in four groups. This was confirmed by 
Hektoen and subsequently adopted by Ottenberg. Moss, in 1910, 
without knowledge of Jansky's work, also found that it is necessary 
to divide bloods into four groups in order to include all individuals, 
but unfortunately employed a system of numbering the groups the 
opposite of that of Jansky. Because of the priority of Jansky's sys- 
tem and its important support by Hektoen and by Ottenberg and 
others, we prefer to use it rather than that of Moss. Groups I and 
IV are transposed in the two systems but Groups II and III re- 
main the same, hence, groups are transposable from one basis to the 
other. The groups are not present at birth, but become established at 
about the end of the first year of life and remain constant thereafter ; they 
are heritable according to the Mendelian law. Disease does not change 
the group of an individual, although, according to some of our experi- 
ments, it seems possible that the agglutinin titer may be somewhat 
reduced by prolonged disease. Jansky included in Group I those 
bloods whose sera agglutinate cells of all other groups and whose 
cells are not agglutinated by any sera; Group IV is the reciprocal 
of Group I in that the sera agglutinate no cells, but the cells are 
agglutinated by sera of all the other groups. Groups II and III are 
reciprocals of each other and occupy intermediate positions between 
Groups I and IV. This may be rendered clearer by the following table : 

Group I. Serum agglutinates cells II, III and IV. 

Cells agglutinated by no sera. 
Group II. Serum agglutinates cells III and IV. 

Cells agglutinated by sera I and III. 
Group III. Serum agglutinates cells II and IV. 

Cells agglutinated by sera I and II. 
Group IV. Serum agglutinates no cells. 

Cells agglutinated by sera I, II and III. 

The following chart presents the classification graphically; the 
-f- sign indicates agglutination : 



I. II. III. IV. 

^ II. + - + - 

3 in. + 

iv. + + + - 



Inasmuch as the Moss classification has been widely adopted we 
include the chart of that system so as to show the relation of the 
two systems of grouping : 


I. II. III. IV. 

I. 4- + + 

5 II. - + + 

HI. + + 


It is of the utmost importance that when the groups are deter- 
mined in any individual the method of classification should be 
clearly stated. 

The incidence of the groups varies somewhat, according to the 
figures of different investigators, and there is probably a factor of 
error due to " random sampling," in spite of the large number of 
individuals examined. Selected figures follow, according to the 

Jansky classification : 






per cent. 


per cent. 


per cent. 


per cent. 


per cent. 


per cent. 


per cent. 


per cent. 


per cent. 


per cent. 


per cent. 


per cent. 


per cent. 


per cent. 


per cent. 


per cent. 


per cent. 


per cent. 


per cent. 


per cent. 


Von Dungern 

Moss 43. 

Olmstead . 
Karsner . . . 
Koeckert . 

Average 42.84 per cent. 41.38 per cent. 10.36 per cent. 5.42 per cent. 

The table shows that about four-fifths of all individuals fall in 
Groups I and II, about equally divided between the two groups, the 
next most frequent being Group III, and the least frequent being 
Group IV. 

Characters of Iso-hemagglutinins. The iso-hemagglutinins are 
neither filterable nor dialyzable, and are destroyed by heat of 62 to 
66 C. for thirty minutes, depending on concentration, i.e., the agglu- 
tinins in high dilutions (1-32, 1-64) disappear at 62 C., and in the 
undiluted sera at 65 to 66 C. They are present in transudates and 
exudates as well as in the plasma and serum, the serum showing a 
greater concentration than the plasma. In serum the titer is usu- 
ally between 1-16 and 1-32, although it may be as low at 1-2, and 
has been reported as high as 1-320, irrespective of group. There is 
variation of agglutinin content and probably of agglutinability of 
cells at different times in the same individual. 

The fact that a blood contains an iso-agglutinin does not nec- 
essarily mean that it will similarly dissolve corpuscles, but the 
converse is true ; namely, that if a serum shows iso-hemolytic prop- 
erties it is also iso-hemagglutinative ; the group relationship prevails 
in both agglutination and hemolysis. In fact, agglutination always 
precedes hemolysis. In spite of this generally accepted view, 
Kolmer claims recently to have demonstrated the presence of iso- 
hemolysins independent of iso-agglutinins. 


The Mechanism of Iso-hemagglutination. Numerous theories 
have been offered, of which we present that of Landsteiner. It has 
recently received support in this laboratory by the painstaking spe- 
cific absorption experiments of Koeckert. Landsteiner considers 
that the division into four groups depends upon the presence, dif- 
ferently distributed in bloods, of two agglutinins, a and b, and two 
agglutinogens, A and B. The distribution of these may be tabulated 
as follows (Jansky classification) : 

Group Agglutinins (serum) Agglutinogens (cells) 

I. a b 

II. b A 

III. a B 

IV. A B 

Aside from the support offered by Koeckert, in his demonstration 
that specific absorption experiments prove the presence of these 
bodies, further confirmatory evidence is found in the fact that the 
agglutinogenic character of cells is demonstrable in the early months 
of life, whereas the agglutinins do not appear until near the end of 
the first year. It is also stated that transfusion with a certain group 
may lead to the development in the recipient of specific iso-agglu- 
tinins for the group injected. Kolmer's work, however, shows that 
immunization of animals with the blood of the various groups pro- 
duces a hemagglutinative and hemolytic serum without group char- 
acters. Karsner and Koeckert have shown that desiccation leads to 
a loss of specificity of the sera, and that at a certain period in the 
desiccation a common agglutinin is found which clumps the cells of 
all groups, including Group I. This is probably in part due to 
alterations in physical character of the redissolved sera, and to 
alterations in hydrogen ion concentration, as shown by Karsner 
and Collins. Therefore, although the Landsteiner hypothesis offers 
an excellent working basis, it seems probable that an intricate 
physico-chemical mechanism is largely concerned in the phenom- 
enon of iso-hemagglutination. 

Iso-hemagglutinins in Lower Animals. The presence of iso- 
hemagglutinins in animals other than man is extremely irregular 
and infrequent. Certainly no classification into definite groups has 
so far been demonstrated. In our own experience the examination 
of from ten to twenty members each of dog, rabbit, cat, and guinea- 
pig species has failed to show iso-hemagglutinins, but others who 
have examined larger numbers have found an occasional instance 
of iso-hemagglutination. 

Relation of Iso-hemagglutinins to Blood Transfusion. The 
principal importance of iso-hemagglutinins and the related iso-hemo- 
lysins in human medicine relates to the transfusion of blood, a thera- 
peutic measure which civil and military practice have shown to be 
of the utmost value in combating secondary anemia following 
hemorrhage. It is also recommended for prolonged sepsis with or 
without severe anemia, for primary anemias, and for certain other 


diseases, but results are not so brilliantly successful as in secondary 
anemias, particularly those resulting from acute hemorrhage. Ill 
effects following transfusion are spoken of as reactions and include 
fever, chills, cyanosis, hemoglobinuria, and even death. Cases com- 
ing to autopsy show parenchymatous degenerations of solid organs, 
marked congestion of all viscera, acute splenic hyperplasia, hemo- 
globin staining, and sometimes multiple small emboli of agglutin- 
ated erythrocytes. Blood studied in life has shown phagocytosis of 
erythrocytes by the recipient's white corpuscles. The reactions de- 
pend in large part on intravascular agglutination and hemolysis, 
but probably certain other factors play a part. The prevention of 
these other factors awaits the determination of their nature, but the 
avoidance of agglutination and hemolysis can easily be accomplished 
by use of the very simple tests for the determination of the presence 
of conflicting iso-agglutinins. The simplest of these tests is the deter- 
mination of the groups to which recipient and prospective donors 
belong. The most desirable means of selection, in our opinion, is 
that whereby the donor is chosen from the same group as the patient. 
Lee and others have maintained that it is equally safe to use members 
of Group I as donors for recipients of any group. The argument in 
favor of this procedure is based on the statement that the real danger 
in transfusion is the use of a donor whose cells are agglutinated by the 
recipient's plasma and that the converse has little or no significance. 
The cells of Group I are not agglutinated by any sera and are, there- 
fore, safe to use. In our own experience we have seen occasional 
reactions following this procedure and prefer to use a donor in the same 
group as the recipient. Reactions following the general use of Group I 
donors do not necessarily mean that the trouble is the result of agglu- 
tination or hemolysis, for, as has been indicated above, other factors 
may be concerned. Nevertheless, it holds true that thousands of trans- 
fusions have been done with Group I as the " universal " donor and 
without reaction. The explanation of the fact that a donor may thus 
be used, whose plasma or serum is capable of agglutinating the recipi- 
ent's erythrocytes in vitro, is not settled, but certain theories have 
been offered. It must be remembered that in transfusion a small bulk 
of blood is introduced, as compared with the total bulk in the recipi- 
ent's body. Therefore, agglutinins introduced in this way are much 
diluted, and as they ordinarily occur in low titer they may be sufficiently 
diluted to be ineffective. Another possibility is that the agglutinins 
are absorbed equally by an extremely large number of cells, each cell, 
therefore, taking up too small an amount to be subjected to agglutina- 
tion. A third possibility is that an excess of non-agglutinable cells 
and the presence of the patient's own plasma permits of the formation 
of only small clumps of cells, so small that they are of no significance 
in the circulation. Our own work has failed to demonstrate anti- 
agglutinins in a large number of tests, and it seems improbable that a 
mechanism of this type operates to protect the recipient. It is conceiv- 
able, however, that these possible factors of safety may not operate and 


reaction follow this type of transfusion. We cannot enter here into 
a discussion of methods of transfusion. 

Methods for Testing Human Blood. The simplest method depends upon 
the preservation in the laboratory of known Group II and Group III sera. These 
should be selected so that they have a relatively high titer, and should not be 
employed if they titrate less than i to 16. The method to be described is essen- 
tially that of Lee and Minot. The apparatus includes a few 7x75 mm. test-tubes, 
a platinum loop, microscope slides with at least one built up on the ends with 
pieces of glass rod or match sticks glued on by means of balsam so that another 
slide may be inverted upon it with hanging drops. A microscope is useful but 
not essential, since a hand lens of 10 diameters magnification is satisfactory. A 
small moist chamber is desirable but not essential. In well equipped labora- 
tories the serum may be kept in the ice chest in sterile ampoules or small bottles 
and drops removed as required. Somewhat more satisfactory is preservation 
in sections of drawn out glass tube similar to that used for vaccine virus. Each 
small tube contains serum for one test and the serum may be blown out exactly 
as is done with vaccine virus. Phenol 0.5 per cent, may be used as a pre- 
servative. One-half cubic centimeter of physiological salt solution is placed in a 
test-tube, and to this are added one or two drops of blood, obtained by ear or 
finger puncture, sufficient to make a slightly opaque emulsion. Clotting of the 
mixture is not harmful since subsequent shaking of the tube will produce a 
homogeneous suspension. Upon a microscope slide are placed one drop each of 
the sera of Groups II and III. With the platinum loop a drop of blood suspension 
is mixed, by gentle rubbing, in each of the serum drops and the slide immedi- 
ately inverted upon the prepared slide or a small rack so as to make hanging 
drops. At the end of five or ten minutes the reaction occurs and may be seen 
with the naked eye; in order to avoid mistakes owing to slight agglutination it 
is important to observe with the 16 mm. lens of the microscope or a hand 
lens. If a small number of specimens is examined it is well to have controls 
with known I, II or III cells. If the reaction is delayed the slide should be kept 
in a moist chamber for one-half hour and then observed. The group to which 
the cells belong is determined by the following section from the chart of 
inter-agglutination : 


i n- = + 

O III. 4- 

IV. + + 

Thus if the cells are agglutinated by both sera they belong to Group IV; if 
not agglutinated at all and the control cells show that the sera agglutinate prop- 
erly the cells belong to Group I; if agglutinated by only III serum they belong to 
Group II, and if agglutinated by only II serum they belong to Group III. 

Hanging drops are not essential, but serve to make the reaction somewhat 
clearer. The reaction occurs with the slides upright. In this case cover slips 
may be used. Many employ undiluted blood and cover with cover slips, but 
rouleaux formation sometimes offers a confusing picture. 

It has been suggested that since the important point of determination is as 
to whether or not the donor's corpuscles are agglutinated by the patient's serum, 
the latter may be separated and placed on a slide with the donor's corpuscles. 
The separation of the serum requires more time than a complete test as given 
above, and is subject to serious error if the patient's serum happens to be of low 
agglutinin titer. 

If standard sera are not available they may be prepared if a known II or 
III blood can be obtained. The interaction of the cells and serum with fifteen or 
twenty other bloods can be worked out on the basis of the chart on inter- 
agglutination. Space does not permit of giving the details, but Brem's method 
gives them accurately. If this cannot be done the method of Rous and Turner 
is probably the best of the methods for use where standard sera are not to be 
had, since this method determines the activity of both the cells and serum of 
the donor and recipient. The method with slight omissions is taken directly 
from the article of Rous and Turner in volume 64 of the Journal of the Amer- 
ican Medical Association. 


" Collection of the Blood. The blood is taken from the patient and the pros- 
pective donors in a i-io mixing pipette, such as is used in counting leucocytes. 
The pipette is rinsed beforehand with 10 per cent, sodium citrate in water; the 
citrate solution is drawn up to the mark i ; the pipette is rapidly filled with blood 
from a puncture of the ear or finger ; and without pause the mixture is expelled 
into a small, narrow test-tube. There is thus obtained a citrated blood containing 
slightly less than i per cent, of citrate. The pipettes which we have employed hold 
only 0.25 c.c. of fluid. This much blood is easily obtained from a single puncture. 
There is no objection to increasing the flow by pressure. Should it cease before 
the pipette is full, the blood must be at once expelled into a test-tube, in order 
that it may mix with the citrate and clotting be avoided. The mixture is then 
taken up again, a new puncture made, and the pipette completely filled. After 
each blood is obtained, the pipette is rinsed with citrate, then with distilled water, 
then with fresh citrate, and it is ready for another blood. If several donors are 
to be tested, two pipettefuls of citrated blood should be obtained from the patient. 
It is best to take them from different puncture wounds, in order to avoid a pos- 
sible clotting in the pipette. 

" Mixing. The mixing is done in pipettes with a capillary end the so-called 
Wright pipettes obtained by drawing out glass tubing in the flame. (Fig. n.) 
The citrated bloods are used as such, and two combinations are made of the 
patient's blood with that of each prospective donor, a mixture containing nine 
parts of the patient's blood to one of the donor's, and a mixture of equal parts 
of the two. The proportions used need be only approximate. In case of 
emergency the first of the mixtures will suffice, since by its use the most 
dangerous possibility, namely, that the blood of the recipient might destroy that 
of the donor, can be ruled out. Following the technic usual with Wright pipettes, 
the capillary tube is marked, blood is drawn to the mark, and each column of 
the blood is separated by an air bubble from the next that is drawn up. To 
insure proper mingling, each mixture should be expelled on a slide, or Widal 
plate, and then drawn high in the pipette, which may be sealed off in the flame 
in case the examination is not to be made for some time. 

" Incubation. No incubation in the ordinary sense is necessary. The pipettes 
are kept at room temperature, and readings are begun after two minutes if 
there is need to hurry. Readings are for agglutination, and even within two 
minutes this is plainly evident, except when the agglutinating forces are notably 
weak. In the final choice of a donor it is safest to rely on results obtained after 
the mixtures have stood for fifteen minutes. But the ruling out of individuals 
with unfit blood may be begun practically at once. 

" Readings. The capillary end of each pipette is broken, a small drop of the 
blood expressed on a slide, a large drop of normal salt solution superimposed 
without mixing, a coverslip put on, and the preparation examined for agglutin- 
ation under the microscope. Fresh preparations can be made at intervals if de- 
sired. The salt solution is not absolutely necessary; but very clear pictures are 
obtained as the blood spreads in it. When agglutination has occurred, the red 
cells show a characteristic clumping, sometimes in small masses, often in large 
ones that are very evident microscopically. 

" If there is no clumping in the preparations made after the mixtures have 
stood fifteen minutes, the assumption is warranted that the bloods do not agglu- 
tinate or hemolyze each other. But if clumping is present in the 9-1 mixture 
and to a less degree or not at all in the i-i mixture, it is certain that the blood 
of the patient agglutinates that of the donor, and may perhaps hemolyze it. 
Transfusions in such cases are dangerous. Clumping in the i-i mixture with 
little or none in the 9-1 indicates that the plasma of the prospective donor 
agglutinates the cells of the prospective recipient. For practical purposes these 
findings suffice. But if there is a desire to know whether both bloods contain 
agglutinins, a 1-9 mixture should be made. If this and the 9-1 mixture show 
large clumps, whereas the clumps are smaller when the bloods are mixed in equal 
parts, two agglutinins must be present. Should there be only one agglutinin, 
little clumping or none will be observed when the blood containing the agglutinin 
is diluted with nine parts of the other blood." 

By the use of the technic indicated in the last paragraph, it is 
possible to overcome error due to weak agglutinin content of the re- 
cipient's blood. This we believe is of especial importance if the 
patient has been ill for a long time. 


Reactions to Transfusion. The effects on the body of introducing 
high titer hemagglutinins have been studied experimentally in normal 
animals and in those which have been splenectomized. In normal animals 
there is found agglutination of red blood-corpuscles with embolism in 
liver, lungs and other viscera. The liver is often found to show hyaline 
necrosis in connection with the emboli. The spleen is large and dif- 
fluent, and there are small areas of necrosis as well as phagocytosis of 
erythrocytes by endothelial cells. Necrosis is also found in the fol- 
licles of lymph-nodes. Multiple hemorrhages may also be noted. After 
splenectomy the phagocytic function of the spleen is taken over by the 
lymph-nodes. The incident hemolysis in either case leads to hemo- 
globinemia and hemoglobinuria, but in splenectomized animals the 
threshold of excretion of hemoglobin is somewhat higher than in 
normal animals. 

In severe and fatal reactions in man the phenomena are not likely 
to be so marked. Phagocytosis of erythrocytes by the recipient's leuco- 
cytes has been observed. We have performed autopsies on twelve 
cases in which transfusion was practised shortly before death, in three 
of which the death was at least in part due to the use of unsuitable 
blood. In all of these the spleen was considerably enlarged (170, 
390, 400 grams), and in one there were multiple small hemorrhagic 
infarcts. One case showed enlarged soft white lymph-nodes. The 
bone marrow was normal in all. All showed marked cloudy swelling 
of the kidneys. Two showed hemoglobinuria, and in one of these 
there was post-mortem staining by hemoglobin. In the case with 
multiple infarcts of the spleen 50 c.c. Group II blood had been given 
to a Group III recipient, and there was neither hemoglobinemia nor 
hemoglobinuria. In the case with hemoglobinemia and hemoglobin- 
uria about 700 c.c. Group III blood was given a Group I recipient. 
Unfortunate accidents led to these errors, and the groups were dis- 
covered subsequent to the operations. In the nine cases where the 
transfusions were satisfactory the spleen was either normal or if 
enlarged was accompanied by septicemia. 

Chemical Agglutination of Erythrocytes. Blood-corpuscles are 
agglutinated not only by various sera but also by certain chemical sub- 
stances. Gay has examined the function of the tonicity of the sur- 
rounding medium in determining iso-hemagglutination and maintains 
that the bloods of that group whose cells are non-agglutinable (Group 
I) are constantly of higher total molecular concentration than the 
other bloods. He further states that a " simple hypertonic solution 
of CaCl 2 , but more particularly solutions hypertonic both in respect to 
NaCl and CaCl 2 , produces a cohesion of any human blood after sev- 
eral hours resembling iso-agglutination." Studies of hypotonic solu- 
tions and of variations of any considerable degree in hydrogen ion 
concentration have been rendered difficult because hemolysis is likely 
to occur under these conditions and render conclusions difficult. Land- 
steiner and Jagic in 1904 were the first to call attention to the fact that 
a well-defined colloid, namely silicic acid, agglutinates erythrocytes. 


Gengou reported agglutination and hemolysis by means of such chemi- 
cal precipitates as calcium fluoride and barium sulphate, but in these 
instances serum served to prevent agglutination. This appears to be 
another example of protective colloidal action. According to Girard, 
Mangin and Henri, the red cells carry electro-negative charges, but 
agglutination has been produced by colloids regardless of the electrical 
charge they carry. We, in collaboration with Hanzlik, have exam- 
ined a wide variety of colloids and have determined that many of 
those which produce thrombosis upon intravenous injection into animals 
also produce agglutination in the test tube. 

Conglutination. Bordet and Gay, as well as Muir and Browning, 
independently described in 1908 the phenomenon of conglutination an 
agglomeration of corpuscles in the presence of two normal sera. The 
result of this reaction is the agglutination of corpuscles, but what is 
known of its mechanism makes it advisable to consider the phenomenon 
after the discussion of hemolysis (see page 126). 


Introduction. The discovery of agglutination led to the discovery 
by R. Kraus in 1897 of the precipitin reaction. His problem was to 
determine whether or not agglutinating sera would act in any way on 
extracts of bacteria, and in his work with typhoid bacilli and cholera 
vibrios he found that the addition of the specific antisera to the bac- 
terial extracts led to the formation of a precipitate and that this 
reaction is specific. This was confirmed by Nicolle. Previously Widal, 
Levy and Bruns had shown the converse, namely, that filtrates of 
typhoid and cholera cultures upon injection led to the formation of 
agglutinins. In 1899 Tchistovichs published the results of his work 
with horse serum and eel serum, demonstrating the formation of 
specific precipitates when the serum of rabbits previously inoculated 
with these sera was added to the antigenic sera. Bordet confirmed 
this with chicken serum and later showed that cow's milk upon injec- 
tion induces the formation of a specific precipitating serum for the 
casein of the milk. Kraus states that previous to the publications of 
Tchistovitchs and of Bordet he had also, in collaboration with Winter- 
berg and E. P. Pick, experimented with proteins of animal origin. 
Fish demonstrated the specificity of various milk antisera for their 
respective antigens. The reaction was enlarged in scope for various 
other animal proteins. Kowarski showed that the reaction is specific 
for higher vegetable proteins as well as for those of bacteria. Certain 
authors have claimed that peptones, globulins, albumoses and other 
protein products are antigenic in a similar manner, but the weight of 
evidence is that the whole protein molecule is necessary. A recent 
review of the literature on this subject by Fink has shown that state- 
ments in regard to the proportion of the entire protein molecule neces- 
sary to take part in the reaction are confusing and obscure. Frequently, 
instead of testing against the decomposition product itself, the serum 
obtained by its use has been tested against the entire protein molecule. 


Fink worked with the precipitates obtained by salting protein solutions 
and found that rabbits inoculated with one-fourth, one-third, one-half, 
and two-thirds saturation products produced no precipitins nor com- 
plement-fixing bodies. In guinea-pigs, however, the three-fourths 
saturated and completely saturated products possess slight sensitizing 
and intoxicating properties, the latter being apparently the more 
active. Nevertheless, three-fourths saturated and completely saturated 
products of egg-white were sufficient to produce definite formation of 
precipitin and complement-binding antibodies but not in as high a titer 
as entire protein. 

Nature of the Reaction. In analogy with the terms used in the 
phenomenon of agglutination Kraus named the antigen, precipitinogen 
and the immune body precipitin. The reaction is similar to agglutina- 
tion in all respects save that here we have to deal with proteins in 
solution. Aging or heating leads to the formation of precipitoids, 
group reactions as well as inhibition zones appear, heat has much the 
same influence in all respects as in agglutination, salts play an im- 
portant part in the reaction and specific absorption can be demonstrated. 
It is known, however, that some protein molecules are largely built 
up of alkaline amino-acids and that others are built up largely of the 
acid amino-acids. Salmine, for example, a product of the spermatozoa 
of certain fish, consists almost entirely of strongly alkaline amino-acids. 
Gliadine of wheat is chiefly built up of dibasic amino-acids, glutaminic 
acid. The fermentation end product of salmine is alkaline and of gli- 
adine acid in nature. An antigliadine serum gives with a homologous 
precipitinogen, a beautiful precipitate, while a mixture of salmine and 
antisalmine-serum gives no visible precipitate. This would indicate 
that the alkaline salts are of importance in the actual formation of the 
precipitins, and we know by simple titration that during the precipitin 
reaction there occurs a reduction of acidity. Nevertheless, it is also 
asserted that when the acidity is due to an organic acid or acid salt 
the reaction appears to be promoted. The precipitin is precipitated in 
the euglobulin fraction of the serum, is destroyed slowly by trypsin 
and rapidly by pepsin. The immune serum contains the precipitin 
which constitutes the bulk of the precipitate, the latter thus represent- 
ing, according to Wells, " the insoluble modification of the previously 
dissolved precipitin and originates chiefly or entirely in the proteins 
of the immune serum." Welch and Chapman obtained, with a precipi- 
tinogen containing only i gram of protein, a precipitate containing 21.1 
grams of protein. Pick employed a precipitinogen which did not give 
the biuret reaction and with this obtained a voluminous albuminous 
precipitate. It must not be understood that precipitins are always the 
result of immunization, for Vaughan states that goat serum contains 
a normal precipitin for rabbit and for dog sera. Such normal pre- 
cipitins are not of very high titer and are not so sharply specific as 
the immune precipitin. Puppies, kittens and rabbits up to ten days 
old may absorb native protein from the milk of the mother which 
apparently stimulates the formation of precipitins. Sera of human 


infants have been observed to precipitate the protein of cow milk. It 
appears possible, then, that from absorption through the intestinal tract 
early in life the protein may appear in the circulating- fluid in native 
form and thus stimulate the formation of precipitins. These, of 
course, are not normal precipitins in the sense indicated above for goat 
serum but similarly are always precipitins of low titer and not 
highly specific. 

Experimental Demonstration. For practical demonstration of the reaction 
the serum proteins are the simplest to use. For immunization of animals the 
intravenous route is by far the best, injecting 2.0 c.c. serum at five-day intervals 
and bleeding ten days after the last dose. Three doses are usually sufficient, but 
five doses frequently give a precipitin of very high titer. In order to get clear 
serum it is necessary to fast the animal for twenty-four hours before bleeding, 
thus eliminating fat from the serum. Rabbits are the animals usually selected 
for this purpose because of their availability in the laboratory and because of the 
relative ease of intravenous injection. Hektoen has shown, however, that the 
domestic fowl is a prompt, reliable and liberal producer of precipitins, even more 
so than the rabbit. A single intraperitoneal injection of 20 c.c. of defibrinated 
blood or serum in most cases yields at the end of ten or twelve days a precipitating 
serum of sufficient strength and specificity for practical purposes; but on ac- 
count of an unwelcome tendency to give non-specific reaction, great care must 
be exercised in all the tests with fowl antiserum, and it is necessary to use 
salt solution 1.8 per cent, in strength. Man is also a good producer of precipi- 
tins, as has been shown by investigation of human serum after the individual 
has been given doses of horse serum. For performing the test, narrow tubes, 
not more than 5 mm. in diameter are most suitable in order to save reagents 
and get clear-cut results. Instead of diluting the antiserum, it is customary 
here to dilute the antigenic serum. Nevertheless the titer thus obtained is 
referred to the immune precipitin. Two methods are in use, the original 
method of actual precipitation, and the Fornet ring test. In either case dilutions 
of the antigenic serum are made i-io, i-ioo, 1-1,000, 1-10,000, 1-100,000, and 
1-1,000,000, with provision for a salt solution control. After such a preliminary 
test the serum may be more accurately titrated with intermediate dilutions. For 
determining precipitation i.o c.c. of each dilution is run into tubes with a nipple 
pipette, and to each is added o.i c.c. immune serum, the latter settling into the 
dilutions, without shaking. Immediate observations are made and then the 
mixtures incubated for one hour at 37 C., followed by subsequent observation, 
and if desirable further observation after twenty-four hours in the ice chest. 
The Fornet ring test is more clear-cut and is more commonly used. Here o.i c.c. 
immune serum is placed in the tubes and the dilutions of antigen added with 
nipple pipettes, so as to form a contact ring as in the Heller test for albuminuria. 
A white ring gradually spreading both up and down indicates a positive re- 
action. A good immune serum titrates 1-10,000 or more, although titers of 
1-100,000 are obtainable. 

The production of bacterial precipitins is somewhat more difficult 
and requires longer immunization, the precipitins appearing, as a rule, 
somewhat later than the agglutinins. Zinsser recommends the use of 
salt solution emulsions of agar cultures killed at 6o-7o C., rather 
than extracts or filtrates of broth cultures. The intravenous route is 
best unless the bacteria are extremely toxic, when the subcutaneous 
or intraperitoneal method may serve. Intravenous injections should 
be given four or five times at five- or six-day intervals, the animal 
(rabbit) being bled eight or nine days after the last injection. Ex- 
tracts of bacteria for similar purposes are obtained by growth for 
three weeks to three months in slightly alkaline broth, filtration through 
Berkefeld filters and injection of the filtrate. Salt solution suspen- 
sions of agar cultures may be shaken in a machine for twenty-four 


hours, filtered through a Berkefeld filter and the filtrate used. Kraus, 
in his original studies, used broth filtrates and also juice expressed 
from the bacteria. Kraus points out that the broth filtrates of toxin- 
producing organisms such as bacillus diphtherise do not precipitate 
when mixed with antitoxic serum. That this is a general rule, how- 
ever, is not true, since Jacoby has shown that it is possible to obtain a 
precipitate by mixing ricin and antiricin serum, and others have ob- 
served similar reaction with the use of abrin and antiabrin serum as 
well as crotin and anticrotin serum. 

The delicacy of the precipitin reaction is great and only exceeded, 
in certain respects, by complement fixation and the anaphylaxis reac- 
tion. It is of interest to note that whereas the Biuret and the Millon 
test for protein will hardly exceed dilutions of i-iooo, the precipitin 
reaction will detect not only the presence of protein but the species 
,f rom which it originates, commonly in dilutions of 1-10,000 or 1-20,000 
and even 1-100,000. 

Physical Basis of Precipitation. The influence of heat on pre- 
cipitation and also the group reactions are of considerable importance in 
the practical application of the phenomenon and will be dealt with more 
fully as this side of the question is considered. The comparisons offered 
between agglutination and certain colloidal phenomena (see page 94) 
are equally applicable to precipitation and require no extensive dis- 
cussion here. It must be borne in mind, however, that the colloidal 
interpretation of these phenomena is not proven. Essentially the same 
arguments are available against the conception of precipitoids as 
against that of agglutinoids, but none of these explains satisfactorily 
the specific absorptive capacities of these hypothetical bodies. As ag- 
glutinogen and agglutinin may exist in the blood of a living animal, 
so may precipitinogen and precipitin coexist. This is compared by 
Zinsser to the fact that if gum arabic is added to a mixture of thin 
gelatin and arsenic trisulphide the precipitation which ordinarily occurs 
will be prevented. The gum arabic in this instance is a protective 
colloid. It is assumed that such a protective colloidal action operates 
to prevent precipitation when precipitinogen and precipitin coexist in 
the blood of a living animal. After the blood is withdrawn and 
allowed to stand, this protective action disappears and precipita- 
tion occurs. 

The fact that precipitin and precipitinogen can coexist in circulating 
blood and that experiments on the attempted production of iso- 
agglutinins with their conflicting results has led to the question of 
whether or not it is possible to produce precipitins in an animal by 
the injection of proteins of a closely related species. Uhlenhuth and 
Weidanz claim to have produced precipitins for human serum by 
injecting human serum into monkeys, the resulting precipitin acting 
on human but not on monkey serum. Berkeley and later Sutherland 
were unable to confirm this experiment and we are forced to the con- 
clusion that precipitin formation in closely related species is by no 
means a constant phenomenon. Such precipitins would be practically 


iso-precipitins, and, as we have seen, their existence is irregular 
and questionable. 

Practical Application. Wladimiroff first applied precipitation 
practically in the diagnosis of glanders in horses, using the serum of 
suspected horses against a filtrate from cultures of glanders bacilli. 
Kraus employed the reaction to identify closely-related bacteria. At 
the present time, however, agglutination is employed for the detection 
of glanders and also for identification of bacteria rather than precipita- 
tion, because the latter procedure introduces the more cumbersome 
technic of obtaining filtrates. 

The Forensic Blood Test. Uhlenhuth and Beumer published their first re- 
sults on the use of the precipitin reaction in legal medicine in 1903. Other 
studies were rapidly contributed, and to-day the method has an established place 
in the identification of stains by blood and other fluids such as seminal fluid. 
If spots on clothing or other material are suspected of being blood, this must 
be proven by chemical, microscopic or spectroscopic examination. Subsequently 
the precipitin test is used to determine the species from which the blood orig- 
inated. Before proceeding to this test it is necessary to have immune pre- 
cipitating serum against the suspected species, usually man, an additional 
immune precipitating serum against some other species and a normal rabbit serum. 
The immune sera are prepared according to the method outlined on page 108. 
The suspected material must be carefully guarded against possible substitution 
or contamination until the immune sera are prepared. It is then dissolved in 
physiological salt solution and a perfectly clear filtrate used. If the material is 
on cloth the latter should be teased so as to permit of solution ; if on some solid 
material, such as a knife blade, it should be scraped off, ground in a mortar and 
a small amount of salt solution added. Cloth should be placed in a test-tube or 
bottle, and it is well to have a control with unstained cloth. The time for 
extraction depends to a certain extent on the freshness of the material, but it 
is wise to allow it to extract in the refrigerator over night, adding a few drops 
of chloroform to prevent bacterial growth. If extraction does not proceed well 
in salt solution it may be necessary to extract with I per cent, potassium cyanide 
solution, correcting the alkalinity after extraction, by means of tartaric acid. 
To prove that the solution contains protein a small amount may be boiled and 
treated with acetic or nitric acid as in the ordinary test for albuminuria. A 
final solution of the suspected material in a dilution of i-iooo is usually em- 
ployed, and this dilution may be approximately determined by the foam test. 
For this purpose make a i-iooo solution of any convenient serum, blow air 
through it in a test-tube and note the persistence of bubbles above the fluid. 
Dilute the extract gradually and blow air through it, repeating until that dilution 
is obtained which will produce a foam of about the same viscosity as that in 
the control tube. If the solution is not perfectly clear it may be centrifuged or 
passed through a filter of washed asbestos or cotton. On the assumption that 
the spot is suspected of being human blood the test is set up as follows : 

Material Result 

Suspected extract -f- anti-human serum + 

Suspected extract 4- normal rabbit serum 
Control extract T anti-human serum 

NaCl solution -(- anti-human serum 

Human serum (i-iooo)-f- anti-human serum -f 

Beef serum (i-iooo) + anti-human serum 
Sheep serum (i-iooo) -(-anti-human serum 

The amounts throughout are o.i c.c. of each reagent, and the test is made 
by the Fornet ring method. Inasmuch as acceptable antisera should titrate 
1-10,000, the reaction in i-iooo dilution occurs within a few minutes, and the 
above result would be interpreted as a clear-cut positive for human blood pro- 
vided the preceding chemical and other tests for blood had been positive. It 
should be remembered that the precipitin reaction in this instance simply iden- 
tifies the material as human protein, and a similar result might be obtained 
from human seminal fluid, albuminous urine, purulent sputum, exudates and 
transudates, unless the preliminary tests had been carried out. 


Biological Relationships. The question of the specificity of this 
reaction has been somewhat confused by quotation from the famous 
studies of Nuttall in regard to interrelationship of species. Nuttall's 
book, published in 1904, was of the utmost importance to biology in 
general, because it demonstrated anew by the use of the precipitin 
reaction the interrelationship of animal species. He showed, for ex- 
ample, the close biological relationships between man and the higher ape, 
also similar relationships in the lower animals, as between the goat 
and the sheep, the horse and the ass. Reference to the tables which 
he published would seem to indicate, however, that the relationship 
between man and the higher ape was so close as to be indistinguishable 
by the precipitin reaction. An example in point is the statement which 
. he makes that whereas human blood will respond to antihuman precipi- 
tating serum to the extent of 100 per cent., the blood of the chimpanzee 
responds to the extent of 130 per cent. These figures, however, refer 
to the bulk of the precipitate thrown down in relation to standard 
dilution of the various bloods employed. He used relatively low dilu- 
tions, allowed the sera to remain in contact for several hours and then 
measured the amount of precipitate. This, as can readily be seen, is 
different from the method which is employed at the present time in 
determining the titer of the sera against the immune serum. The 
latter method is distinctly more delicate in determining the specificity 
of the reaction. For that reason it is the method employed in the for- 
ensic test of to-day, as well as in ordinary laboratory procedures. Fur- 
thermore, we find at the present time that the test demonstrates its 
specificity particularly in the presence of strong sera by reading very 
shortly after the contact has been made. Hektoen offers an excellent 
example of this in the following table (antihuman serum) : 


Fish i-io 

Chicken i-io 

Rabbit o 

Guinea-pig i-io 

Rat i-io 

Cat i-io 

Dog i-io 

Swine i-io 

Sheep i-io 

Beef i-io 

Horse i-io 

Goat i-io 

Monkey (Macacus rhesus) i-ioo 

Human 1-5000 

It will be noticed by reference to the above table that the titer of 
the serum used in this particular test was only 1-5000, and we would 
expect an even greater difference between the titer with the different 
animal sera if the antihuman serum had been of higher titer. Con- 
cerning the group reactions in the precipitin test an interesting instance 
is given by Hamburger in regard to the action of the serum of a 
rabbit inoculated simultaneously with sheep serum, goat serum and ox 
serum, all of which are fairly closely related to each other biologically. 


The serum of the rabbit when mixed separately with each of these 
three antigenic sera gave the most voluminous precipitates in the 
presence of the sheep serum, less in the presence of the goat serum 
and least in the presence of the ox serum. This observation has been 
confirmed by Arrhenius. Just why the sheep antiserum should be 
the most powerful is difficult to say, but it might be assumed that the 
sera of closely-related species may augment the antigenic power of 
the strongest of the three species used. Of further interest, Hektoen 
has shown that in rabbits previously injected with foreign serum the 
subsequent injection of a different serum may reawaken the production 
of precipitin for the antigen previously injected. The practical value 
of this fact is that rabbits which have once been used for the production 
of precipitin should not be used again for the same purpose with 
another protein because of possible decrease in specificity of the 
second antiserum. 

Organ Specificity. The question of organ specificity is of con- 
siderable importance in the discussion of the specificity of the precipitin 
test. Numerous experiments have been made by various immunological 
methods to determine whether or not it is possible to identify the 
protein of a given organ within the same species. It may be stated 
very briefly that these experiments have not met with any great degree 
of success. However, in regard to the protein of the crystalline lens 
of the eye and the protein of the testicle, certain interesting facts have 
been discovered. Immunization with protein extracts of the crystalline 
lens will produce precipitating sera which operate not only on the 
lens protein of the same species but on the lens protein of all animals 
as low in order as fish. In this example the species specificity has been 
entirely replaced by a curious organ specificity. The organ specificity 
in this case is so strict that the immune serum will not react with other 
tissue extract even of the same species. Lens protein may, indeed, be 
injected into the same species from which the lens was taken and give 
rise to specific precipitins. By the use of the complement-fixation test 
it has further been shown that in adult human beings it is possible to 
detect the presence of an antibody for lens protein which is not detect- 
able in children. This phenomenon will be mentioned later in con- 
nection with the autocytotoxins (see page 142). Zinsser comments to 
the effect that biologically these phenomena probably signify that al- 
though there are fundamental species differences between the general 
body proteins of various animals, there are still in certain highly spe- 
cialized organs varieties of protein which possibly because of functional 
exigencies have developed similar chemical characteristics. In regard 
to the testicle and the placenta, it might be supposed that the germ char- 
acter of these tissues is retained as distinctive from the somatic char- 
acter of the other body tissues. This would not apply to crystalline 
lens, since it is not of germ character. On the other hand, although 
the lens can be regarded as a highly-specialized organ in both morpho- 
logical and physiological senses, the testicle and the placenta can 
hardly be so considered. Such discussions are likely to be fruitless 


until it is possible to isolate the protein of other body organs without 
contamination by the animal's blood. Up to the present time this 
seems to be impossible. Studies by Bell, for example, with perfusion 
of various organs has demonstrated the impossibility of removing the 
blood completely. 

Detection of Food Adulteration. The precipitin reaction is ap- 
plied not only to detect blood as indicated above but also various other 
body proteins; for example, it may be used to detect the nature of 
bone fragments or other tissue scraps. Of great significance is the 
fact that the precipitin test is employed for the detection of adultera- 
tion of food products. It has been utilized, for example, in detecting 
adulteration of sausages by the use of horse and other meats. In the 
preparation of such food products, heat is often employed, and there- 
fore it is necessary to know the influence of heat on the precipitin 
reaction. The relation of heat to the agglutinin reaction has already 
been discussed (see page 93), and it is found that similar conditions 
exist in regard to the precipitin test. Obermeier and Pick studied this 
problem experimentally and found that an anti serum, even of high titer, 
produced by an unheated antigen, failed to precipitate when brought 
into contact with heated serum. If, however, animals are immunized 
with serum boiled for a short time, the resulting immune serum forms 
a precipitate when brought in contact with either heated serum or 
unheated serum. Therefore, the precipitin produced by the latter 
method is regarded as more comprehensive in its precipitating activity, 
but nevertheless its species specificity remains unimpaired. By em- 
ploying a lower degree of heat, namely 70 C., Schmidt found that 
this marked difference was not so apparent and that an immune serum 
prepared by injecting unheated serum would produce precipitation 
with unheated serum and with the moderately-heated serum. How- 
ever, the titer of antiserum prepared by the use of moderately-heated 
antigen was not as high as with the use of unheated antigen. Schmidt 
ifurther found that he could produce an even more comprehensive 
immune serum by boiling the antigen until a coagulum was formed, 
namely, for three hours. The coagulum was washed with salt solution, 
dried, powdered and then taken up with a normal NaOH solution. 
Zinsser and Ottenberg found that the use of a boiled antigen led to 
the production of a comprehensive precipitin, but nevertheless they 
determined that this resulted in some loss of specificity of the precipitin. 

This outline of the influence of heat will serve to show that in the 
detection of the adulteration of food products extreme care must be 
taken in the selection of material. Wherever possible, fresh material 
should be obtained, and the material for testing should always be taken 
from near the middle of the specimen. This precaution prevents con- 
tamination with other meat, and in the case of sausage yields material 
likely to be less influenced by heat or smoke. The meat is cut into fine 
pieces and allowed to extract in salt solution. Clarke used 30 grams 
meat and 50 c.c. physiological saline, extracting in the ice chest for 
twenty-four hours, and further diluting 1-300 for the test. Such 


extracts must be proven as to protein content by the nitric acid test and 
the foam test. Violent shaking is to be avoided, because it liberates 
fats and lipoids which cloud the extract. If precipitation occurs by the 
use of this extract with an immune serum prepared by injecting un- 
heated protein, the test can be regarded as highly specific. If, however, 
it is necessary to use serum which is prepared by injecting heated pro- 
tein, the specificity cannot be regarded as being so high. In practice 
it is the rule to use serum prepared by injecting unheated protein rather 
than otherwise, unless the special indications of the case indicate the 
use of an immune serum prepared from heated antigen. The technic 
in case of food adulteration is essentially the same as for the detection 
of blood. Inasmuch as the specificity of this reaction is a species speci- 
ficity, it is satisfactory to utilize the animal's serum for immunization 
rather than extracts of the flesh under suspicion. 

In mixtures of meat such as one finds in sausages, the mixture in 
itself sometimes interferes with the delicacy of the test. In these 
cases it has been found that the complement-fixation test is likely to 
give more satisfactory results. 

The precipitin test is also applied in the enforcement of game 
laws. For example, cases arise in which the unlawful possession 
of venison is suspected, and the identity of the meat may be estab- 
lished by the precipitin reaction. 

Numerous suggestions have been made regarding 1 the identification 
of racial strains within species, but we agree with Hektoen in saying 
that "suggestion to the contrary notwithstanding, it is not possible 
to distinguish between different human races, and far less between 
individuals, by means of the precipitin test." 

Function of Precipitation in Immunity. The function of pre- 
cipitation in the protection against infection is not clear, and, indeed, 
according to certain theories, it may play a part in hypersusceptibility. 
Friedberger has shown that the addition of complement to a precipitin- 
precipitinogen mixture leads to the formation of a toxic body, but there 
is no convincing evidence that this actually takes place in the living 
animal (see page 218). It is to be considered possible, on the other hand, 
that a certain amount of protection against foreign proteins may depend 
on precipitation, the precipitate being less harmful and more suscep- 
tible to the destructive action of ferments. 




















Introduction. In the study of resistance to disease it was learned 
very early in the course of the investigations that the blood serum 
possesses the property of destroying bacteria. Later it was found that 
blood serum may possess similar power in regard to other cells, in- 
cluding various animal cells, particularly the erythrocytes. Rather 
than consider the subject of cytolysis in a historical fashion, we believe 
that it may be much more clearly discussed by first presenting the 
established facts which have been learned concerning the power of 
blood serum to destroy red blood-corpuscles. Many substances other 
than blood serum may destroy erythrocytes and immunology has 
profited from the study of hemolysis resulting from chemical and 
physical agents, but the greatest advance has been made by the investi- 
gation of the hemolytic properties of the blood. 

Hemolysins. Hemolysins are classified, in the same manner as 
hemagglutinins, into autohemolysins, iso-hemolysins and hetero- 
hemolysins. These may be present normally or may be produced as a 
result of immunization. Landois in 1875 studied those normal hetero- 
hemolysins which for years have made blood transfusion a dangerous 
operation and showed that fresh sera from various species possess the 
power of dissolving or laking the erythrocytes of certain foreign species. 
In 1898 Belfanti and Carbone noticed that the serum of a horse which 
had received numerous injections of rabbit blood was, upon injection, 
specifically toxic for rabbits, but they did not determine the cause of 
the toxicity. In the same year Bordet published his discovery of the 
fact that several injections of defibrinated rabbit blood into the peri- 
toneal cavity of guinea-pigs led to the production of an immune body in 
the guinea-pig serum capable of rapidly laking rabbit erythrocytes, 
whereas normal guinea-pig serum possesses the same property in only 
slight degree or not at all. Shortly afterward von Dungern and Land- 
steiner independently published similar results. The immune body 
in the serum has been named hemolysin and also hemotoxin, but the 
former term has received much wider usage, because the constitution 
of this body is not that of true toxins, because the effect is seen on the 
blood-corpuscles rather than the whole blood, and because the hemo- 
globin is liberated for solution in the surrounding medium without 
actual destruction of the stroma. Bordet in his study of the subject 
showed that heating the serum to 55 C. for thirty minutes so altered 
it that it no longer produced hemolysis; in other words, it became 
" inactive." It could, however, be reactivated by the addition of a 
small amount of fresh normal serum. This indicated that two sub- 
stances are concerned in the hemolytic activity of blood serum, a 
thermostable substance present in the immune blood and a thermolabile 
substance present in normal blood as well as in immune blood. Bordet 
named the immune thermostable body " substance sensibilisatrice " and 
Buchner named the thermolabile body " alexine." Ehrlich and Morgen- 
roth, whose studies have been of fundamental importance, named the 
thermostable body " amboceptor " and the thermolabile body " com- 
plement." Others have given other names, but these two forms of 


nomenclature are most frequent in the literature. We have elected to 
use the terms amboceptor and complement because of our belief that 
these terms have attained the more widespread usage. Complement 
appears in the blood of many species, but may be very small in amount 
or absent from certain species. Certain complements may operate 
with the amboceptors of only a few species, whereas others may act 
with amboceptors of a large number of species. Within a given species 
different individuals may possess complement in variable quantity, and 
it may vary at different times in the same individual. The complement 
of guinea-pig blood is usually large in amount and applicable to the 
amboceptors of a considerable number of other species. Complement 
does not appreciably change in amount by the ordinary processes 
of immunization. 

Immune Hetero-hemolysins. Hemolytic amboceptors may be 
natural to a blood or may be developed by immunization. Autolysins 
and isolysins may be produced but with great difficulty and variability. 
Isolysins may be present normally, notably in man. Heterolysins may 
be found normally and can be readily produced by artificial immuniza- 
tion. Bordet produced heterolysins by intraperitoneal injection of ery- 
throcytes. They may also be induced by the subcutaneous and by the 
intravenous routes of inoculation. Two important conceptions of the 
mode of action of the amboceptor have been proposed. Bordet, Metch- 
nikoff and the French school consider the action to be in the nature of a 
sensitization or fixation of the antigenic cells, so that they are more 
readily acted on by the complement, in somewhat the same fashion 
that a mordant prepares a cell so that it will stain more readily. Ehr- 
lich and Morgenroth and the German school consider the amboceptor 
as a link which brings together antigen and complement ; in other words, 
in their conception the amboceptor possesses two binding groups, a 
cytophilic and a complementophilic group, each capable of acting as a 
specific receptor. In order to discuss the various theoretical con- 
siderations more clearly, it is essential that the well-established facts in 
regard to hemolysis be presented as they are ordinarily demonstrated 
in a practical way. 

Preparation of Immune Hemolysins. The Blood Antigen. In immuniza- 
tion for the production of a hemolysin it is necessary to select the animals to 
be used. The rabbit is usually chosen as the animal to be immunized because 
of the fact that it is easily available, relatively inexpensive, and yields a fairly 
large amount of blood. In selecting the animal whose blood-corpuscles are to 
be used for the production of hemolysin, convenience again plays a part. The 
sheep is the animal most commonly employed, although the goat is equally use- 
ful. Reasonably large amounts of blood can be secured from such animals at 
short intervals of time, without deleterious effects. Dog blood is unsatisfactory 
because the corpuscles do not resist standing for any length of time. The cat is 
undesirable because of its relatively small size. In order to secure blood from 
a goat or sheep the animal is either strapped on a board, or may be held by a 
skilled attendant. The neck is shaved over the jugular vein, the area washed 
with soap and water, cleansed with alcohol, and the vein distended by pressure 
over the jugular bulb at the base of the neck. The blood is collected through a 
fairly large needle into a sterile flask containing glass beads or fragments of 
glass tubing. Rotation of the flask or shaking during the collection and con- 
tinued shaking for five or ten minutes after the collection completely defibrinates 


the blood. The blood may be injected as defibrinated blood for purposes of im- 
munization, but as a rule in order to avoid any influences the serum may have, 
the blood is washed so that only corpuscles are injected. For purposes of washing 
50 c.c. centrifuge tubes are desirable, but if these are not obtainable, the 15 c.c. 
size may be employed. The blood is measured into the tube with a pipette, 
usually to the amount of 5.0 c.c. The amount of blood is marked with a 
grease pencil and the tube filled with physiologic salt solution. The tube is 
centrifuged until the blood is thrown down. The supernatant fluid is poured off 
and the tubes again filled with salt solution. The sedimented corpuscles are 
shaken up into the salt solution and again centrifuged. This operation is re- 
peated again, and the blood is said to have been washed three times. Aiter 
the last centrifugation the supernatant fluid is poured off and the sedimented 
blood-corpuscles restored to original volume by addition of salt solution. In 
order to make a five per cent, suspension, this is washed into a 100 c.c. cylinder 
and made up to 100 c.c. volume with salt solution. Any other percentage 
desirable may be made by appropriate additions of salt solution to the original 
blood mass. 

Preparation and Collection of Immune Sera. The injection into the rabbit 
may be by subcutaneous, intraperitoneal, or intravenous routes. The intravenous 
route produces immune bodies most rapidly, as has been shown by Bullock, 
.and as a rule produces an immune serum of higher titer than is obtainable by 
other methods. An excellent way to produce hemolysin rapidly is to inject in- 
travenously into the rabbit three doses 4.0 c.c. each of 50 per cent, suspension 
of washed sheep or goat erythrocytes at intervals of five days. The method of 
intravenous injection has previously been described in connection with the pro- 
duction of agglutinins (see page 82). A test bleeding may be made from the 
posterior ear vein five to seven days after the last injection, and if the titer of 
the serum is not sufficiently high, one or two more injections may be given. When 
sufficiently high the rabbit is bled from the femoral artery as previously 
described (see page 83). The blood is collected in a flask, the flask inclined 
at an angle of about 45 until the blood is firmly clotted. The flask is then placed 
in an upright position in the refrigerator for about twenty-four hours, after 
which the collected serum is pipetted into a sterile container. Melick, in a study 
of the influence of colloidal suspensions on the production of hemolysis, finds 
that if he gives preliminary intravenous injection of aleurpnat suspension and 
subsequently immunizes with blood-corpuscles, the hemolytic sera are of con- 
siderably higher titer than in animals not so treated. 

Titration of Immune Sera. For titration of the hemolysin in the rabbit 
serum, it is necessary to have a 5 per cent, suspension of the antigenic corpuscles, 
the serum to be tested and irf addition fresh guinea-pig serum which serves as 
complement. In such a titration the 5 per cent, suspension of corpuscles and the 
complement are regarded as standards and employed in the same doses through- 
out the series of tubes. If 0.5 c.c. of serum and 0.5 c.c. of corpuscle suspension 
are employed, 0.05 c.c. of complement is usually sufficient, Before attempting 
the titration the rabbit immune serum should be inactivated by heating in a 
water bath at 56 C. for one-half hour. Dilutions of the inactivated immune 
amboceptor are made as a rule i-io, i-ioo, 1-500, i-iooo, 1-1500, 1-2000, 1-2500, 
1-3000, 1-4000. The guinea-pig serum (complement) is diluted i-io. The follow- 
ing protocol will show how the series of tubes is set up : 

5 ^hee SP cells n Amboceptor Complement i-io Result 

0.5 c.c. -zoo 0.5 c.c. 0.5 c.c. CH 

0.5 c.c. -500 0.5 c.c. 0.5 c.c. 

0.5 c.c. -looo 0.5 c.c. 0.5 c.c. 

0.5 c.c. -1500 0.5 c.c. 0.5 c.c. 

O.5 C.C. -2OOO O.5 C.C. O.5 C.C. 

0.5 c.c. -2500 0.5 c.c. 0.5 c.c. CH 

0.5 c.c. -3000 0.5 c.c. 0.5 c.c. PH 

0.5 c.c. -4000 0.5 c.c. 0.5 c.c. 

0.5 c.c. 0.5 c.c. 0.5 c.c. 

0.5 c.c. i-ioo 0.5 c.c. 

The last two tubes are controls and should be made up to volume by addi- 
tion of 0.5 c.c. saline in place of amboceptor in the one and of complement in the 
other. The letters CH indicate complete hemolysis, PH partial hemolysis, and 




FIG. 12. o shows a saline suspension of blood-corpuscles before 

hemolysis; 6 the same after hemolysis. a' and V present the 

appearance of a and b after sedimentation of corpuscles. From 

Noguchi, Serum Diagnosis of Syphilis. 

20 units of Ambocepfar 
used //? e<ac/i comDination 

Green = Complement 
Purple Amboceptor 
Red = r/aemo/ysis 

I unit ofAmboceptor 
used in each with various 
fractions ofa complement 


N no hemolysis, the reading being made after a period of incubation in the 
water bath at 37 C. This period may be thirty minutes, one hour or two hours, 
but subsequent experiments with the same system of amboceptor, complement 
and corpuscles must be made with the same period of incubation as practised in 
the original titration. In this laboratory one hour is the standard time for incu- 
bation. In order to make results somewhat more clear-cut, the rack of test 
tubes may be placed in the refrigerator over night and the results read the fol- 
lowing morning. The lapse of twelve or eighteen hours time permits the cor- 
puscles to settle to the bottom of the test-tube ; therefore any red coloring of 
the supernatant fluid may be interpreted as a partial or complete hemolysis, de- 
pending on the depth of color and the amount of sediment remaining on the 
bottom of the tube. The controls which are used in this experiment demon- 
trate that neither complement nor inactivated amboceptor will produce hemoly- 
sis. The result given in the above experiment indicates that at some point 
between the dilutions 1-2500 and 1-3000 the exact end point of titration is to be 
found. In order to determine the exact end point it is well to set up an addi- 
tional series with dilutions of 1-2500, 1-2600, 1-2700, 1-2800, 1-2000. and 1-3000 
with the necessary controls. If it is found that complete hemolysis takes place 
in a dilution 1-2700 and not in the dilution 1-2800 the dilution 1,2700 is taken as 
the end point or titer. The unit of amboceptor therefore is 1-2700 of 0.5 c.c. or 
1-5400 of i c.c. In the experiment outlined above, the unit of amboceptor would 
be designated as 0.5 c.c. of a 1-2700 dilution of the immune serum. 

Titration of Complement. As has been indicated previously, the amount 
of complement in guinea-pig serum varies in different animals. Therefore sub- 
sequent experiments with this amboceptor must be controlled by titrating the 
complement. This may be done by setting up a series of tubes as follows, the 
control tubes being made up to volume with salt solution : 

Erythrocytes Amboceptor Complement Result 

suspension 1-2700 i-io 

0.5 c-c. 0.5 c.c. 0.5 c.c. CH 

0.5 c.c. 0.5 c.c. 0.4 c.c. CH 

0.5 c-c. 0.5 c.c. 0.3 c.c. PH 

0.5 c-c. 0.5 c.c. 0.2 c.c. N 

0.5 c.c. 0.5 c.c. o.i c.c. N 

0.5 c.c. ... 0.5 c.c. N 

0.5 c-c. 0.5 c.c. ... N 

0.5 c-c. ... ... N 

In this experiment it is found that 0.4 c.c. of the new complement is sufficient 
for activating the unit of amboceptor. Therefore, whereas in the first experiment 
0.5 c.c. i-io complement dilution was the unit of complement, in the second experi- 
ment 0.4 c.c. i-io dilution complement is the unit. If it is found that in none of 
these tubes complete hemolysis takes place because of weak complement, it will 
then be necessary to set up an additional series with complement diluted 1-5 
instead of i-io. 

Quantitative Relations of Amboceptor and Complement. The 
quantitative relationship between the amount of complement and ambo- 
ceptor used has been very extensively studied. It is now known that 
a larger amount of complement will require a smaller amount of ambo- 
ceptor for the production of complete hemolysis in the standard blood- 
corpuscle suspension and conversely a smaller amount of complement 
requires a larger amount of amboceptor. Thus, if we use two units of 
complement, hemolysis will occur in the presence of less than one unit 
of amboceptor. If we use two units of amboceptor, it will require 
less than one unit complement to produce complete hemolysis. This 
relationship, however, is not in definite proportion. For example, if 
four units of amboceptor are employed, one-third unit of complement 
is necessary. This relationship is beautifully illustrated in the dia- 
gram (Fig. 13) taken from Noguchi. 


Quantitative Relations of Amboceptor and Antigen. By subse- 
quent studies of different mixtures, it was found that the unit of 
standard corpuscle suspension can take up considerably more than one 
unit of amboceptor. This amount varies with the total quantity of im- 
mune body present. For example, Muir found that on addition of 
twelve doses of amboceptor one dose remained free, on addition of six- 
teen doses of amboceptor two doses remained free, on addition of 
twenty doses three doses remained free and on the addition of twenty- 
three doses of amboceptor, four doses remained free. When, how- 
ever, the mixture of complement, amboceptor and red blood- 
corpuscles is properly adjusted, the reaction completely uses up the 
amboceptor, complement and, by hemolysis, all the red blood-corpuscles. 
Correspondingly, if two units of complement are employed in the 
presence of one unit of amboceptor, it does not follow that after 
the reaction one unit of complement will remain free. As a matter 
of fact, practically the entire two units of complement will be utilized 
in the reaction. Nevertheless, increasing the amounts of complement 
will leave more and more complement free in the supernatant fluid. 
These points will be made somewhat clearer after subsequent experi- 
ments have been outlined. 

Relative Affinities of Amboceptor and Complement. In the in- 
troductory paragraph it was pointed out that the amboceptor has a 
special affinity for the antigenic red blood-corpuscles, but that the com- 
plement has no such affinity. This is illustrated by the fact that when 
red blood-corpuscles are set up against amboceptor they will absorb 
the amboceptor, but if they are set up in the presence of complement 
they will not absorb complement. 

The following experiment illustrates this point: Two centrifuge tubes 
are marked A and B. In tube A are placed i.O c.c. standard erythrocyte sus- 
pension (5 per cent, suspension) and i.O c.c. inactivated immune serum so 
diluted as to contain two units amboceptor. This tube is incubated at 37 C. 
for thirty minutes and then centrifuged. The supernatant fluid is pipetted 
into a tube marked A 2. The erythrocyte sediment in tube A is washed in 
salt solution, again centrifuged and the supernatant fluid discarded. The 
sediment in tube A is resuspended in i.O c.c. salt solution and two units of 
complement, i.e., i.o c.c. i-io dilution are added. To tube A 2 are added two 
units complement (i.o c.c. i-io dilution) and i.o c.c. 5 per cent erythrocyte 
suspension. These tubes are incubated for one hour at 37 C. Tube A will 
show hemolysis because the sedimented corpuscles have absorbed ambo- 
ceptor and the addition of complement is sufficient to complete the reaction. 
Tube A 2 will not show hemolysis because the amboceptor is not in the 
supernatant fluid and the complement is not sufficient to lake the added 
corpuscles. At the same time the converse or the foregoing experiment may 
be conducted. In tube B are placed i.o c.c. standard erythrocyte suspension 
(5 per cent, suspension) and i.o c.c. fresh guinea-pig serum diluted i-io. 
This is incubated thirty minutes at 37 C, centrifuged and the sediment 
washed. The supernatant fluid is placed in tube 62. The sediment in tube B 
is resuspended in i.o c.c. salt solution and i.o c.c. immune serum so diluted 
as to contain two units amboceptor is added. To the supernatant fluid in 
tube B 2 are added i.o c.c. immune serum (two units amboceptor) and i.o c.c. 
erythrocyte suspension. These tubes are incubated for one hour at 37 C. 
Tube B 2 will show hemolysis because the supernatant fluid after the centrifu- 
gation still contains complement, so that the addition of amboceptor and 
erythrocytes permits of completion of the reaction. Tube B will not show 


hemolysis because the corpuscles in the sediment have not taken up any 
complement, and the addition of amboceptor is not sufficient for the 
reaction to occur. 

Selective Absorption of Amboceptor and Complement. Not only 
is it possible to show, as has been done in the preceding experiment, 
that red blood-corpuscles will combine with amboceptor and not with 
complement, but if conditions are so arranged that hemolysis is pre- 
vented, it is possible to demonstrate that red blood-corpuscles will 
selectively absorb amboceptor from a mixture of amboceptor and 
complement. In order to prevent hemolysis, it is necessary to permit 
the absorption to take place at o C. Not only must this precaution 
be observed, but the tubes must be cooled, the various reagents in the 
mixture must be cooled in advance and the centrifuge carrier must 
also be cooled. 

The various reagents are placed in test tubes and all the tubes placed in 
a mixture of salt and ice. Into a cold centrifuge tube are placed i.p c.c. 
5 per cent, erythrocyte suspension, i.o c.c. inactive immune serum so diluted 
as to contain two units amboceptor and i.o c.c. guinea-pig serum, i-io dilu- 
tion. This tube remains in the salt-ice mixture for thirty minutes and is 
then centrifuged. The supernatant fluid is poured off and divided so that 
one-half the amount is placed in each of two tubes. The sediment is washed 
in cold salt solution and resuspended in 4.0 c.c. cold salt solution. These 
4.0 c.c. are divided between two tubes. The four tubes so prepared are set 
up as follows: 


Supernatant fluid 1.5 c.c. 

Fresh guinea-pig serum, i-io 0.5 c.c. 

5 per cent, erythrocyte suspension 0.5 c.c. 

TUBE 2. 

Supernatant fluid 1.5 c.c. 

Immune rabbit serum 0.5 c.c. 

5 per cent, erythrocyte suspension 0.5 c.c. 

TUBE 3. 

Sediment 2.0 c.c. 

Fresh guinea-pig serum, i-io 0.5 c.c. 

TUBE 4. 

Sediment 2.0 c.c. 

Immune rabbit serum 0.5 c.c. 

These tubes are incubated for one hour at 37 C. Inasmuch as the 
supernatant fluid no longer contains amboceptor, tube i will fail to show 
hemolysis, but in the case of tube 2 the amboceptor is added, and since the 
supernatant fluid contains complement which has not been absorbed by the 
corpuscles, hemolysis will result. The sediment has absorbed amboceptor 
from the mixture ; therefore, in the case of tube 3, the addition of fresh guinea- 
pig serum will serve to produce hemolysis. The sediment has not, however, 
taken up any complement, the addition of the immune serum in tube 4 will 
not serve to complete the reaction, and hemolysis will not occur. By the 
use of sera containing other hemolytic amboceptors, it is possible to show 
not only that absorption of amboceptor may occur from a complement 
amboceptor mixture, but that this absorption is specific for the particular 
amboceptor concerned. 

Influence of Amount of Complement. Although, as will be shown 
subsequently, the concentration of complement plays a part in the com- 


pletion of hemolysis it can be demonstrated that the absolute amount 
rather than the degree of concentration is of importance in regard to 
the amboceptor. 

This may be shown by placing in each of four tubes 0.5 c.c. 5 per cent, 
suspension of corpuscles and adding to the second, third and fourth tubes, 
respectively, four, nine and fourteen volumes of salt solution. To each of the 
four tubes is added one unit amboceptor, and the mixture incubated at 37 C. 
for one-half hour to permit absorption of amboceptor. The tubes are cen- 
trifuged and the supernatant fluid is discarded. To each tube is added i.o c.c. 
complement so diluted as to contain one unit, and the mixtures again incu- 
bated at 37 C. for one hour. Hemolysis will occur equally in all tubes 
showing that the complete absorption of amboceptor by the cells occurred 
in spite of marked dilution in some of the tubes. 

Rate of Absorption of Amboceptor. The absorption of ambo- 
ceptor varies in rapidity under different conditions. For example, 
absorption takes place more readily at 37 .C. than at 20 C., and more 
readily at 20 C. than at o. An exception to this rule appears in 
cases of paroxysmal hemoglobinuria. Some of these cases possess in 
the blood an autohemolysin which does not enter into combination with 
erythrocytes at body temperature. If the blood is withdrawn and 
placed at a temperature of o to 10 C. for an hour the cells absorb the 
amboceptor and subsequent incubation at 37 C. permits the inter- 
action of complement so that hemolysis results. With this and 
possibly some other exceptions the general rule holds true that tem- 
peratures approaching 37 C. favor the union of amboceptor and antigen. 
Certain physical conditions also play a part in rapidity of absorption 
as may be shown by the following experiment in which the mixture of 
corpuscles and amboceptor is made under different conditions. 

Two wide test tubes or small beakers are marked A and B. In A are 
placed six units of cell suspension; namely, 3.0 c.c. 5 per cent, suspension. 
To this are added drop by drop 3.0 c.c. amboceptor, so diluted that it con- 
tains six units, the tube being shaken constantly during the addition. In 
tube B the process is reversed, the amboceptor being placed in the tube and 
the cell suspension added drop by drop. These mixtures may be titrated 
against varying amounts of complement in a series of tubes, or six units of 
complement may be added to tube A and tube B. An hour's incubation at 
37 C. will show less active hemolysis in tube B than in A. The probable 
explanation is that the first cells added to the amboceptor in tube B absorb 
all or nearly all the amboceptor, and the subsequently added cells are only 
partly saturated or take up no amboceptor at all. 

This experiment illustrates the very rapid absorption of amboceptor 
by cells and also the fact that cells may absorb considerably more than 
one unit of amboceptor. 

Dissociation of Amboceptor-Antigen Union. Whereas tempera- 
tures up to 37 C. appear to favor absorption of amboceptors, Bail, 
Tsuda and others have shown that a temperature of 42 C. results in 
a partial dissociation of amboceptor. That dissociation of amboceptor 
and cells could occur was shown independently by Muir and by Mor- 
genroth. Muir mixed i.o c.c. 5 per cent, corpuscle suspension with 
ten units amboceptor and allowed the mixture to stand at room tem- 
perature for one hour. The tube was then centrif uged, the corpuscles 


washed three times and resuspended in salt solution to a volume of i.o 
c.c. To this was added i .o c.c. untreated corpuscle suspension, the tube 
shaken and placed at 37 C. for one hour. At the end of this time 
four units of complement were added, the tube incubated again for 
one hour and complete hemolysis was found. Thus it was found that 
the original cells yielded at least one unit of amboceptor for the new 
cells. Although in the report cited on page 120, twelve units gave one 
free unit, Muir states that usually one unit of amboceptor can be 
obtained from corpuscles containing six units. In this experiment the 
dissociation was at 37 C., but dissociation takes place at room tem- 
perature, although more slowly, and at o C. it is practically nil. By 
working with sensitized cells and with supernatant fluids, it is possible 
to titrate the latter so as to determine the exact quantities of ambo- 
ceptor dissociated. Kosakai, in working with so-called pure hemolysins, 
has recently shown that the antigen and amboceptor union is reversible to 
a greater extent than has previously been supposed. He main- 
tains that the reversibility under these circumstances is almost or 
quite complete. 

Specificity of Amboceptors. Group Reactions. The hemolytic 
amboceptors are highly specific, but show, as do other immune bodies, 
group reactions. Ehrlich and Morgenroth showed that immune sera 
prepared against ox blood are hemolytic also for goat and sheep blood 
and that a hemolysin prepared against goat blood also dissolves ox 
blood. Marshall showed that an antihuman hemolysin acts on monkey 
blood and vice versa. In any case the hemolysin is most active in the 
presence of the antigenic corpuscles. Treatment of a hemolytic im- 
mune serum with heterologous corpuscles removes more of the specific 
immune body than is the case in other group reactions. For example, 
Muir developed an anti-ox-blood serum which, in a dose of 0.0005 c.c. 
dissolved i.o c.c. 5 per cent, suspension ox corpuscles and, in a dose 
of 0.0012 c.c. dissolved a similar suspension of sheep corpuscles. Ab- 
sorption by sheep corpuscles in excess reduced the titer against ox cor- 
puscles so that the serum dissolved the latter in doses of 0.0012 c.c. ; 
in other words, the titer of the serum was reduced to about half its 
original strength. Ehrlich and Morgenroth showed that if the quantity 
of sheep corpuscles is carefully adjusted so as exactly to equal the 
hemolytic power for such corpuscles, the fraction of amboceptor lytic 
for sheep corpuscles may be absorbed without reducing the titer against 
ox cells. If, however, the amboceptor for ox blood is removed by 
absorption with ox corpuscles the hemolytic power for sheep corpuscles 
is entirely destroyed. Thus it is seen that there is close similarity with 
the group reactions of agglutinins and other immune bodies. Ehrlich 
and Morgenroth explain the phenomenon by assuming that each ambo- 
ceptor contains numerous " partial amboceptors " formed in the im- 
mune animals in response to relatively undifferentiated receptors of the 
antigenic cells. In other words, ox-blood corpuscles are supposed to 
contain a certain number of receptors specific to those cells, and in 
addition other receptors that are closely similar to or identical with 


certain receptors of sheep cells and goat cells. Therefore, the injec- 
tion of ox cells leads to the production of an amboceptor containing 
partial amboceptors specific for ox blood and partial amboceptors 
specific for the common receptors of ox, sheep and goat cells. The 
removal of the partial amboceptors common to all three cell receptors 
will not remove that specific for ox cells, but ox cells will remove both 
the specific and common fractions. This explanation has been the 
subject of much experiment, particularly with anti-hemolysins, and 
modern views are not entirely in accord with the original views of 
Ehrlich. The subject will be referred to again in connection with a 
discussion of anti-amboceptors and anti-complements. In the same 
place will be found a discussion of the interpretation of the ambo- 
ceptor as made up of a cytophilic and complementophilic group. 

Nature of the Antigen. In ordinary practice the entire erythrocyte 
is employed for immunization, but attempts have been made to deter- 
mine what fraction of the cell is truly antigenic. Ford and Halsey 
have shown that the use of either stroma or the laked hemoglobin may 
serve to produce hemolysins, but they obtained only questionable results 
following the use of pure hemoglobin. Stewart obtained essentially 
the same results. Nucleo-proteins obtained from dog blood are capable 
of producing specific hemolysins. Pearce and his co-workers have 
shown that nucleo-proteins from washed organs also lead to the forma- 
tion of hemolysins specific for the homologous species. Organ and 
cell extracts free from blood also serve as hemolysinogens ; the best 
example is an extract of spermatozoa, for in this instance there is 
no question of blood contamination of the extract. Of further interest 
is the fact that ether extracts of erythrocytes, alcohol-ether extracts, 
and extracts in 1.5 per cent, sodium bicarbonate induce the formation 
of weak hemolysins without the coincident formation of hemagglu- 
tinins. This indicates that the hemagglutinin and hemolytic ambo- 
ceptor are probably separate and distinct antibodies. 

Nature of the Amboceptor. The amboceptor, although it resists 
heat of 56 for one hour or more, is injured by heat of 60 C. for twenty 
minutes, is almost completely destroyed by 70 C. for one hour and is 
completely destroyed by boiling. Like antitoxin, it does not dialyze, 
is electro-positive and is resistant to ultra-violet rays. It is carried 
down in the euglobulin fraction of the serum protein, but by various 
methods of purification may be obtained in an almost protein-free 
state. The method of purification described by Kosakai is of im- 
portance from various points of view and deserves some description 
at this point. He requires a hemolytic serum which titrates 1-10,000. 
This is diluted to 100 times its volume with salt solution and 5 c.c. of 
the diluted serum are poured into 4 c.c. blood-cell suspension. The 
union of amboceptor and red cells is accomplished by exposure at room 
temperature for fifteen to twenty minutes, after which the cells are 
freed from serum by repeated washing. To the antigen-amboceptor 
combination is added isotonic or slightly hypertonic aqueous solution 
of a sugar such as saccharose, glucose or lactose, and the mixture incu- 


bated at 55 C. for fifteen to twenty minutes, during which period it 
is shaken several times. The mixture is centrif uged and the supernatant 
fluid placed in a separatory funnel with five to ten volumes of ether 
and shaken for one or two hours until the solution becomes quite 
colorless. The saccharose solution is separated from the ether and 
dialyzed in running water in order to free it from sugar and salt. 
After dialyzation the solution is concentrated in a vacuum until it 
reaches the original volume of blood serum employed. Strong salt 
solution may prevent amboceptor from entering into combination with 
complement, but it does not interfere with the amboceptor cell union. 
Alkalis may prevent either form of union and may serve partly to 
dissociate amboceptor cell combinations. 

Mechanism of Operation of the Amboceptor. As has been 
pointed out previously, the action of amboceptor is differently inter- 
preted by the Ehrlich and the Bordet schools. If the Ehrlich view of 
the two-fold binding group is to be adhered to, it should be possible to 
show on the one hand a combination with antigen, and on the other 
a combination with complement. Of these possibilities there is no 
doubt that combination with cells is possible, but as yet no conclusive 
evidence has been produced to show a combination between comple- 
ment and an amboceptor not united to its antigen. The discovery of 
the Neisser-Wechsberg phenomenon (see page 147) was regarded as 
demonstrating a combination between free amboceptor and comple- 
ment. This explanation, however, does not take into account the 
possible relationship to certain colloidal reactions such as have been 
described in connection with the inhibition zone of strong agglutinins 
and is therefore not to be regarded as settled. Ehrlich and Morgen- 
roth stated that if amboceptor is repeatedly injected into animals an 
anti-amboceptor is produced which serves to combine with the cytophilic 
group of amboceptor, but Bordet found that a normal serum, free from 
hemolytic amboceptor could be used to produce the same immune body, 
and argued therefrom that this antibody could not be regarded as a 
specific receptor. Ehrlich and Sachs admitted the fact of Bordet's 
experiments and came to the conclusion that the substance is anti- 
complementophile, rather than anti-cytophile. As will readily be seen 
this argument presupposes the correctness of the Ehrlich conception 
of amboceptor, and is therefore not to be accepted as conclusive. With- 
out the actual demonstration of the union of free amboceptor and 
complement, the union of antigenic cells and amboceptor is of quite as 
much value in support of the Bordet view of sensitization as in support 
of the Ehrlich hypothesis. Nevertheless, Ehrlich and Sachs have 
reported what they believe to be a crucial experiment in that it appears 
to show that at least in some instances free amboceptor and comple- 
ment may combine. Horse serum is slightly hemolytic for guinea-pig 
erythrocytes and ox serum is somewhat more so. If inactivated ox 
serum and fresh horse serum are added to guinea-pig cells, hemolysis 
occurs, the ox scrum acting presumably as an amboceptor, the horse 
serum as complement. If the guinea-pig cells are treated with inac- 


tivated ox serum for a time ordinarily sufficient for amboceptor ab- 
sorption, washed free of serum and then treated with fresh horse 
serum as a complement, no hemolysis occurs. Furthermore, under 
these conditions no hemolytic immune body has been absorbed from 
the ox serum. Hemolysis only occurs when fresh horse serum and 
inactivated ox serum are added as a mixture. The interpretation is 
that in this particular hemolytic system the amboceptor must be com- 
bined with complement before the amboceptor combines with the cells, 
or, in other words, that the complementophilic group of a free ambo- 
ceptor has united with complement independently of the cyto- 
philic group. 

Conglutinin. Bordet and Gay have studied the phenomenon de- 
scribed in the preceding paragraph and have come to a different 
conclusion as to interpretation because of their discovery of a 
so-called " bovine colloid " in the ox serum. They attribute the 
hemolysis in the Ehrlich-Sachs phenomenon almost entirely to the 
amboceptor and complement of the horse serum. The complex 
of guinea-pig cells and the two bodies in the horse serum serves 
to attract the bovine colloid which augments the complementary action 
of the horse serum so as to produce complete hemolysis and at the same 
time produces marked agglutination of the cells. This colloid is 
thermostable, is probably of protein nature, unites with a complex of 
cells, amboceptor and complement, but does not act upon either normal 
cells or cells saturated with amboceptor. Bordet and Streng in a later 
study named the colloid " conglutinin." Streng found that the same 
phenonemon could be demonstrated in regard to bacteriolysis and that 
conglutinin is present in the sera of the ox, goat, sheep and certain 
other herbivora but not in the sera of the cat, dog, guinea-pig, or bird. 
Sachs and Bauer have not offered a better explanation of the phe- 
nomenon unless the German theory of amboceptor is unqualifiedly 
accepted. In our opinion both sides of this controversy deserve the 
most careful consideration and much light may be thrown by further 
study. The more modern views of immunological processes, influenced 
as they are by the great advances in colloidal chemistry, tend toward 
acceptance of the Bordet hypothesis of sensitization of antigen by the 
thermostable constituent of cytolytic sera, at least until and unless 
more conclusive contradictory evidence can be produced. 

Complement. Distribution. Complement is that thermolabile ele- 
ment of normal blood which in the presence of amboceptor and antigen 
completes the cytolytic reaction. As regards hemolysis, complement 
in the presence of hemolytic amboceptor causes solution of the red 
blood-corpuscles and thus renders the reaction visible. Complement 
is found in the blood and in lesser amount in nearly all the other body 
fluids except the aqueous humor of the eye. It is also found in inflam- 
matory exudates and sometimes in transudates, but it is not present 
in the urine, nasal secretion or the secretion of other glands except 
that of the breast (milk). The amount in the blood is fairly constant 
for any given individual, but during the first twenty-four hours after 


birth the complement content of the blood has been found to be rather 
small ; Gay has found it to be somewhat less in women than in men. 
Moro has found it to be less in bottle-fed than breast-fed babies. 
Although individual variation may be great, there is a certain uni- 
formity in different members of the same species. This is true through- 
out a large number of species, except the horse, in which species it is 
found to vary markedly. Different species as such contain different 
amounts of complement. The guinea-pig contains, as a rule, more 
complement per cubic centimeter than other species. Man and rabbit 
contain less than the guinea-pig, and in the case of the mouse it is 
very difficult to demonstrate any complement at all. It has recently 
been found that insects and mollusks contain practically no complement. 
Alterations of Amount of Complement. The amount of comple- 
ment in a given blood may be made to vary by artificial means. For 
example, the injection of indifferent materials, such as foreign blood 
plasma, bouillon, aleuronat, pepton, yeast, nuclein, physiological salt 
solution, produces an increase in the amount of complement, but this 
increase is not permanent. Similarly complement may be increased for 
a short time following the injection of pilocarpin, phlorizin, staphylo- 
cocci, oil of turpentine and thyreoidin; exposing an animal to high 
temperatures may also increase complement. Although it is generally 
true that complement is not increased by immunization, nevertheless 
Cantacuzene has recently shown that by injecting red blood-corpuscles 
into certain marine invertebrates he is able to increase the amount of 
complement in their blood. Complement may be reduced temporarily 
by the injection of sodium taurocholate, potassium picrate, toluylendi- 
amin and more permanently by experimental phosphorus poisoning, 
experimental chronic suppuration, starvation and by alcohol poisoning. 
If sensitized blood-cells, i.e., blood-cells saturated with amboceptor, 
are injected into an animal, it can be demonstrated that the amount of 
complement is reduced by the hemolysis which takes place in vivo. 
Shaw has found that in the case of recently acquired syphilis, although 
the blood before treatment shows no alteration of complementary ac- 
tivity, yet the administration of salvarsan may reduce this activity 
to a considerable degree. The experimental investigations of the effect 
of disease in man on the complement content of his blood are very 
unsatisfactory because human blood normally contains only a small 
amount of complement and the detection of any variation is susceptible 
to a wide margin of experimental error. 

Method of Obtaining Complement. Complement is usually obtained 
from the guinea-pig, although under special circumstances it may be obtained 
from other animals. The blood may be withdrawn in any manner adapted to 
such a procedure. In the case of the guinea-pig the method employed in this 
laboratory is to anesthetize the animal very slightly, pull the hair from the 
neck, make a longitudinal slit in the mid-line of the neck, place a 15 c.c. centri- 
fuge tube toward the upper end of the slit with its lip firmly pressed into the 
opening, then with a scissors snip the carotid artery, carefully avoiding the 
trachea. The animal is then held head downward while the blood drains into 
the tube. The blood is allowed to clot in the tube and the clot separated from 
the side of the tube with a long sterile or clean needle, as the necessity of the 
case indicates. The clot separates best at room temperature, but if centrifuga- 


tion cannot be done immediately the clot may be allowed to separate in the 
ice chest. As soon as the serum has separated out of the clot, the tube is 
centrifuged and the serum collected by means of a pipette. If guinea-pigs are 
large, the blood may be collected in smaller quantities by heart puncture or by 
bleeding from an ear vein, thus obviating the necessity for killing the animal. 

PIG. 14. Method of obtaining blood from guinea-pig (See text). 

Origin of Complement. Considerable controversy has been waged 
concerning the origin of complement since the time that Hankin and 


subsequently Metchnikoff expressed the belief that complement origin- 
ates in the leucocytes of the body and is only liberated upon the death 
of these cells. Metchnikoff used the term cytase to indicate what we 
now call complement and believed that the microphages gave rise to 
a microcytase capable of dissolving blood and other body cells. Pf eiffer 
and certain other German workers take a diametrically opposed posi- 
tion and maintain that the leucocytes furnish none of the complement in 
the blood. A. von Wassermann and also Landsteiner believe that the 
leucocytes may constitute one source of origin for the complement, 
and it seems practically certain from modern investigations that several 
organs play a part in the formation of complement. Before the bac- 
tericidal action of blood was thoroughly understood as due to the inter- 
action of amboceptor and complement, certain studies seemed to indicate 
that exudates rich in leucocytes were active as bactericidal agents, but 
it is now understood that other constituents of the exudate take part 
in this phenomenon and more recent experiments show that extracts 
of leucocytes do not yield a complement. It has been shown further 
that variations in the total leucocyte count in an animal produce no 
corresponding variations of complement content. Neuf eld and certain 
others take the view that even inside the living leucocytes there is no 
complement because they have found that destruction of red blood- 
corpuscles within living leucocytes takes place at a distinctly slower 
rate of speed than is the case in ordinary hemolysis. Furthermore, 
they point out that the method of destruction is quite different, in that 
ordinary hemolysis shows simply liberation of hemoglobin without 
destruction of the stroma. Metchnikoff's belief that the death of the 
leucocytes yields complement was supported by an experiment which 
apparently showed that complement is present in serum after clotting, 
but not in plasma. A considerable amount of experimental evidence 
has been adduced, since this statement of Metchnikoff, to show that 
plasma contains complement in the same amount as does serum. Some 
of these experiments appeared to be invalid on the ground that im- 
munological work with a plasma is likely to lead to coagulation, thus 
producing a serum for the actual experiments. After these objections 
had been presented, further experiments were performed which over- 
came such objection, and it now seems perfectly clear that plasma con- 
tains complement. This fact has been firmly established by the 
recent work of Watanabe. 

Nature of Complement. Complement is probably of protein 
nature, inasmuch as it is destroyed in coagulation of the serum by heat 
and is digested by trypsin. Noguchi and his co-workers were of the 
opinion that complement is a combination of soap and a protein, but 
numerous other workers failed to confirm these studies. This state- 
ment of Noguchi, as well as the work of Kyes, with cobra venom led 
to the hope that it might be possible to prepare an artificial complement. 
Landsteiner and Jagic have investigated the question and have shown 
that whereas it is possible to substitute for amboceptor a colloidal 
solution of silicic acid, which nevertheless shows none of the specific 


characters of amboceptor, it is absolutely impossible up to the present 
time to offer any substitute for complement. Complement resembles 
an enzyme in that it is thermolabile, disintegrates cells, does not pass 
through Berkefeld filters, is adsorbed by kaolin and destroyed by 
shaking. Furthermore, it activates amboceptor much in the same 
manner as entero-kinase activates trypsinogen. As against the idea that 
complement is an enzyme is the fact that in the reaction of hemolysis, 
hemoglobin is liberated without destruction of the stroma of the cells 
and the further fact that complement acts quantitatively, following in 
a general way the law of multiple proportions. As is well known, heat 
at 56 to 60 C. for one-half hour destroys the complementary activity 
of a serum. It has recently been shown, however, that if heat of 
56 C. is applied for only a short period, i.e., from seven to ten minutes, 
the complementary action is restored after several hours have elapsed 
(the phenomenon of Gramenitski). Tru's is interpreted as due to an 
agglomeration or aggregation of protein particles resembling heat 
coagulation of protein. The restoration of activity after standing is 
ascribed to a dispersion of the protein aggregates so that they can 
act nearly or quite as they did originally. Ultra-violet rays destroy 
complement, but it is stated that X-rays do not. Recent work in this 
laboratory by Ecker has shown that the visible spectrum also serves to 
reduce complementary activity. Experimental conditions in this in- 
stance made it possible to work with three divisions of the spectrum, 
namely, a division near the violet end, a division in the middle of the 
spectrum and a division near the red end. It was found that those rays 
toward the violet end of the spectrum were more active than the 
rays in the middle of the spectrum and the latter were more active 
than the rays at the red end of the spectrum. That this is a function of 
the wave-length of the ray is not absolutely certain but seems probable 
in view of the work of Bovie, Brooks and others, which shows that the 
presence of cells in the serum reduces the activity of the ultra-violet 
rays. That the destruction, however, is a function of the penetrability 
of the rays is not borne out by the statement that X-rays fail to 
destroy complement. We have also been able to show in this lab- 
oratory that drying of complement produces some deterioration. Other 
workers have stated, however, that if the complement is mixed with 
a proper concentration of salt, preferably about 8 per cent, and then 
dried, the salting nullifies the destructive action of desiccation and 
the dried serum under these circumstances may be preserved for a 
considerable period of time. Complement may be inhibited by the 
presence of hydroxyl ions but is restored to activity by the addition of 
hydrogen ions. Complement can be made to combine with magnesium, 
calcium, barium, strontium and sulphate ions and can be separated by 
simple chemical precipitation. Acids and alkalis in sufficient concen- 
tration also serve to destroy complement. 

Preservation of Complement. Owing to the extreme lability of 
complement, the question of prolonged preservation assumes consid- 
erable importance. The fresh serum may be desiccated in air, in 


vacuum, in vacuum after freezing, or on filter paper. In the hands of 
certain workers various methods of this sort have proven more or 
less successful but do not seem to be widely applicable. It is of im- 
portance to keep in mind that under such conditions the desiccation 
of serum does not remove the possibility of the destructive action of 
light. Other methods of preservation include salting with sodium 
chloride and also with sodium acetate. The former has been fairly 
successful, but the latter has been completely abandoned. Another 
method is salting and then freezing, but this has been found to be in 
no way superior to freezing without salting. According to Bigger, 
it is of extreme importance that the serum should be sterile to ensure 
the success of any method of preservation. Browning and Mackie have 
found that frozen serum kept at a temperature of -15 C. retains its 
complementary power three months without appreciable loss. Noguchi 
and Bronfenbrenner found that at 10 C. the serum loses one-half 
its original strength at the end of twenty-four hours. If it is kept at 
37 C. it loses two-fifths of its strength at the end of six hours; at 
45 C. one-half hour exposure reduces it to one-third to one-half its 
original strength ; at 50 C. 50 per cent, is lost in five minutes. They 
have examined the rate of destruction at 55 and find that this goes 
on quite irregularly and is not in proportion to the length of time. 
The irregularity, however, presents a certain rhythm, i.e., a period of 
greater destruction alternating with a period of less active destruction. 
Reudiger has studied the preservation of frozen complement and finds 
that at the expiration of one week whether the complement is made 
up of serum of a single guinea-pig or the pooled serum of several 
guinea-pigs the activity in the Wassermann is somewhat stronger than 
with fresh serum. At the end of two weeks the frozen complement 
gives results that are practically identical with the results obtained 
with fresh complement, but after two weeks the frozen complement 
gradually loses strength apparently more rapidly in mild weather than 
in very cold weather. 

Variability of Complement. Complementary activity varies con- 
siderably in different sera ; in the same serum it may operate differently 
with amboceptors from several different species. The explanation of 
this difference of activity has led to a difference of opinion as to the 
exact nature of the complementary activity. Ehrlich and Morgenroth 
and the German school take the position that a given serum contains a 
considerable number of complements, whereas Bordet and his school 
take the point of view that the complement in any given serum is a unit, 
although they admit that complements in different sera may represent 
a somewhat different constitution. 

Multiplicity of Complements. Ehrlich and Morgenroth were able 
to show that the complementary activity of a serum could be divided 
by means of filtration in the following respect. They showed that 
complement for sensitized guinea-pig cells passes through the filter, 
whereas complement for sensitized rabbit cells remains in the filter. 
It has also been shown by thermal and chemical differentiation that 


some complements are destroyed and others remain in the same serum. 
Weak acids and weak alkalis may differentiate complement similarly; 
it is stated that digestion by papain also serves so to differentiate. By 
injection of a complementary serum into foreign species, a so-called 
anti-complement is obtained which is said to act upon one of the 
complements of a serum and not upon others, irrespective of whether 
the complement of the antigenic serum or of some other serum be em- 
ployed in the subsequent test. Practically all these experiments have 
been performed in such a way that the complement acts with normal 
amboceptors and the question at once arises as to whether or not the 
same phenomena would be observed with immune amboceptors. Even 
in the case of normal amboceptors, there is experimental contradiction 
of the original supposition of Ehrlich and Morgenroth. Neisser stated 
that anthrax bacilli deprive fresh rabbit serum of its bactericidal com- 
plement, but not of its /hemolytic complement. Wilde showed that if 
a sufficient mass of anthrax bacilli were added to the fresh rabbit serum 
all the complement is used, so that further bactericidal action does not 
occur and no hemolytic action can be demonstrated. Similarly Bordet 
found that unsensitized red blood-corpuscles deprive a serum of only 
part of its complement^ but that cells strongly sensitized with hemolysin 
use up all the complement both bactericidal and hemolytic. He believes 
that the reason normal amboceptors do not utilize all the available 
complement is due to the fact that such normal amboceptors do not suf- 
ficiently sensitize the antigenic cells. Therefore, the complete sensitiza- 
tion of the cells will result in a complete utilization of complement. 
After the publication of these experiments, Ehrlich, who confirmed the 
results, explained the phenomenon as being due to a multiplicity of 
complements in the serum. In order to do so, he was obliged to alter 
the original conception of the amboceptor, so that instead of having 
a single cytophilic group it must contain several cytophilic groups. 
Therefore, the term was altered to polyceptor instead of amboceptor. 
The polyceptor was supposed to have one group with an especial affinity 
for a dominant complement and other receptors with affinities for the 
secondary complements. If the dominant complement is absorbed by 
the polyceptor, the secondary complements are also involved, but, on 
the other hand, if, as has been claimed, it is possible to obtain a serum 
with only secondary complements present, these may be absorbed 
without action upon the receptor for dominant complement. This expla- 
nation, however, rests entirely upon the Ehrlich conception of the ambo- 
ceptor, and, inasmuch as this conception is not conclusively proven, it 
is not necessary to accept the idea that complements are multiple. This 
question, however, is not settled at the present time, and reference 
will be made to it again in connection with the phenomenon of com- 
plement fixation. 

Complementoids. The similarity in action and nature of comple- 
ment and toxin was early recognized, and it was therefore attempted to 
determine whether or not complement could be broken up in the same 
way as toxin so as to form complementoids. If such were the case, it 


should be possible to break up a complement so as to demonstrate a 
haptophore group and a zymophore or zymotoxic group. Thus, ex- 
posure to increased temperature might be so arranged as to destroy 
the zymophore group and leave the haptophore group intact. If this 
were true, the haptophore group or complementoid might be added to 
an antigen-amboceptor mixture and thus prevent any further action 
by a fresh whole complement. Experimentally, however, it was found 
that this, in the majority of instances, does' not occur. Nevertheless, 
Ehrlich and Sachs found that if they mixed inactivated guinea-pig 
serum, normal inactivated dog serum and guinea-pig cells, hemolysis 
did not occur, even after the addition of fresh guinea-pig serum. They 
believed this to be the result of a blocking or plugging of the com- 
plementophile group of the dog amboceptor by the complementoid of 
the inactivated guinea-pig serum, thereby preventing the union when 
fresh active complement was added. Fuhrmann supported this state- 
ment and maintained that allowing the complement to stand for a 
period of three weeks was even more adapted to separation of the hapto- 
phore and zymophore group. Following this work, Muir and Brown- 
ing conducted an extensive series of complicated experiments, which 
in the main tend to support the view of Ehrlich that complementoids 
actually exist. If they do exist, however, they are not uniformly demon- 
strable, and it may very well be that this is due to the difference in 
destructibility of the two groups being so slight that our methods of 
differentiating by means of heat and standing are not sufficiently exact. 
Complement Fractions. Further light was thrown on the possi- 
bility of fractioning complement by the experiments* of Ferrata, who 
found that dialyzation of the serum resulted in the destruction of com- 
plementary activity. Dialyzation precipitates the so-called globulin 
fraction of the serum as contrasted with the albumin fraction which 
remains in solution. The precipitate may be dissolved in physiological 
saline and the portion in solution may be restored to its original salt 
concentration, thereby forming isotonic solutions of the two protein frac- 
tions. Ferrata found that neither of these components in the presence of 
an amboceptor was capable of producing hemolysis, but that if both were 
added, sufficiently soon after dialyzation, hemolysis would take place. 
Brand studied this phenomenon further and found that both fractions 
are equally thermolabile and because of activities which he discovered, 
named the fraction contained in the globulin precipitate " mid-piece " and 
that in the albumin " end-piece." If the amboceptor-cell mixture is 
treated first with mid-piece, no hemolysis occurs, but if end-piece is then 
added, hemolysis occurs as it would have in the original amount of com- 
plement. If the end-piece is first added and later the mid-piece, hemo- 
lysis will occur, but in very much smaller degree than if the entire 
complement had been used. Zinsser found, however, that when mid- 
piece and end-piece are mixed and then added to the sensitized cells, 
the hemolytic effect is reduced and is considerably less than if mid-piece 
is added before end-piece. It has been found that the mid-piece may 
enter into combination with the sensitized cells at o C, but the end- 


piece combines only at considerably higher temperatures. It has also 
been found that the mid-piece of one animal species may be activated 
by the end-piece of another animal of the same or different species. 
Nevertheless, Ritz and Sachs have shown that the serum of an animal 
may possess a mid-piece for certain sensitized erythrocytes, but does 
not necessarily possess a corresponding end-piece. Marks has studied 
the quantitative relations of mid-piece and end-piece and has found that 
a ratio of i-i is not necessarily the optimum for hemolysis and that 
very often it is necessary to change the ratio; this change must be by 
increase of mid-piece, never by increase of end-piece. If the two 
are mixed before addition to the amboceptor-cell mixture, an excess 
of mid-piece inhibits hemolysis, but if the excess of mid-piece is added 
first followed by end-piece, hemolysis is complete. Brand and later 
Hecker found that if the globulin precipitate is preserved dry or in 
solution in distilled water it will retain activity for several days, but in 
physiological salt solution it loses its activity in three to four hours. 
This, however, does not indicate destruction of mid-piece in salt solu- 
tion since it will combine with sensitized cells if added before end- 
piece. Marks holds that this phenomenon is due to the inhibition of 
hemolysis by excess of mid-piece and does not occur if proper pro- 
portions are maintained in the mixture. Swirski maintains that the 
complement fixation of the Wassermann test binds mid-piece but not 
end-piece. This has been investigated by Bronf enbrenner and Noguchi, 
who believe that the free end-piece in Wassermann tests differs from all 
other end-pieces in that it activates the complex which includes sheep 
cells but has no effect upon the cells of other animals. Bessemans has 
recently investigated again the question of thermostability of end-piece 
and mid-piece. He finds that there are important differences in certain 
of the sera he has examined, so that a general statement in regard to the 
heat resistance of these fractions is not justified. 

Browning and Mackie have found that by various methods of f rac- 
tioning the serum it is possible to divide complement into four frac- 
tions and that certain combinations consisting, as a rule, of at least three 
of these reproduce quantitatively the full hemolytic effect of the whole 
complement. This presents numerous intricate possibilities of experi- 
ment, but the important point is that such a demonstration makes the 
use of the terms mid-piece and end-piece no longer desirable. 

Normal Hetero-hemolysins. The preceding discussion has been 
concerned chiefly with complement and immune amboceptor. Histori- 
cally much study had been directed toward the normal cytotoxic powers 
of blood serum before the immune amboceptors were recognized; 
Fodor, Nuttall, Nissen and Buchner had investigated the action of nor- 
mal sera in dissolving bacteria. Buchner in 1893 pointed out a similar 
capacity of blood serum for dissolving animal cells, particularly ery- 
throcytes. Ehrlich and Morgenroth took up the question as to whether 
or not the globulicidal activity of normal serum is due to an interaction 
of two substances similar to that in immune sera. They showed that 
normal dog serum is capable of dissolving guinea-pig erythrocytes, but 


that it is inactivated by heating to 55 C. Reactivation by fresh dog 
serum was undesirable because of the normal amboceptor present. 
Therefore, they employed fresh guinea-pig serum in fairly large doses 
and reactivated the heated dog serum so that complete hemolysis oc- 
curred. Thus they demonstrated the double nature of the normal 
hemolysins and also that a complement may serve to hemolyze cells 
of the same species from which the complement is obtained. Other 
experiments have shown, however, that a complement operates less 
actively against homologous cells than against heterologous cells. Ehr- 
lich and Morgenroth. showed similar relationships by employing as the 
amboceptor normal calf serum and normal sheep serum, as well as 
similar hemolytic complexes with sheep and goat blood. They also 
showed that in a number of instances the amboceptor could be dif- 
ferentially absorbed by cells at o C., leaving complement free in the 
serum. Such absorption could not be accomplished with all normal 
hemolytic sera; in some the cells absorbed both amboceptor and com- 
plement, whereas in others no absorption whatever occurred. They 
interpreted the absorption of both bodies as due to the possession on the 
part of the amboceptor of equal avidity of both the cytophile and com- 
plementophile group, whereas failure of absorption was supposed to be 
due to a stronger affinity of complement for amboceptor than of cells 
for amboceptor. We record the fact without accepting the explanation, 
but it is important that in some instances normal hemolytic sera may 
fail to exhibit a separability of complement and amboceptor by means 
of differential absorption. 

A normal serum may be hemolytic for cells of more than one species ; 
this is true of goat serum, which is hemolytic for both guinea-pig and 
rabbit cells. In such cases it is possible to absorb one amboceptor, leave 
the other active in the serum and thus demonstrate multiplicity of 
specific amboceptors in a serum. Ehrlich and Morgenroth also main- 
tained that in the case of goat blood there is a different complement for 
the two types of cells, but as has been indicated in discussing comple- 
ment this possibility seems unlikely. 

Proportions of Amboceptor and Complement in Normal 
Hemolysins. Further difference between a normal and immune 
hemolytic serum lies in the different proportion of amboceptor and 
complement. In a normal hemolytic serum the amount of amboceptor 
present is small and the complement is usually present in at least suf- 
ficient quantity to saturate the amboceptor ; it may be present in excess. 
In immune sera the amboceptor is increased enormously, whereas the 
complement is not altered in quantity. Therefore, such an immune 
serum may contain amboceptor in greater quantities than can be sat- 
urated by complement and for its full activity requires more com- 
plement than can be furnished in the immune animal's serum. This 
increase in amboceptor is out of all proportion to the amount of antigenic 
cells injected. Muir, for example, calculated that in immunizing a 
rabbit the total amount of ox blood injected was 30 c.c., and hemolytic 
amboceptor was produced sufficient to dissolve the erythrocytes in 


6000 c.c. of ox blood. The practical bearing of the disproportion of com- 
plement to immune amboceptor lies in the use of bactericidal sera. It 
is easily conceivable that injections of such sera may meet in the injected 
animals' blood with an insufficient amount of complement for complete 
activation. Therefore, it may be advisable in such experiments or in 
therapeutic use of sera of this type to activate with a sufficient quantity 
of fresh complementary serum. 

Normal Iso-hemolysins. Attention has been called (page 99) to 
the phenomenon of iso-hemagglutination. Similarly iso-hemolysins 
can be demonstrated. For such a purpose the serum must be fresh 
and the corpuscles exposed to it at incubator temperature. It is prob-- 
able that these hemolysins resemble other normal hemolysins. The 
groups correspond to the groups of iso-hemagglutinins. As in other 
experiments with hemolysins, agglutination appears and is followed 
by hemolysis. Agglutination inhibits hemolysis to a certain degree, as 
has been shown by Handel and by Karsner and Pearce. Kolmer, Trist 
and Flick have maintained in a recent study that there are two varieties 
of natural hemolysin and hemagglutinin in human sera. They find a 
thermolabile variety of these antibodies which is destroyed at 56 C. 
for thirty minutes and a less thermolabile or thermostable body which 
is destroyed at 62 C. for thirty minutes. Exposure at 56 C. removes 
the various iso-hemolysins but does not destroy the iso-hemagglutinins. 
Sands and West have found that if the immune sera are filtered (more 
particularly in I 10 dilution) through perfectly clean Kitasato or Cham- 
berland filters a large amount of the hemagglutinin is removed, with 
slight or no reduction of hemolytic activity. In fact, the hemolytic 
activity may be increased by the filtration and this may be explained 
as due to the removal of whatever inhibiting power on hemolysis 
hemagglutination may display. 

Anti-amboceptors. Inasmuch as the bodies which take part in 
hemolysis, the amboceptor and complement, are of protein nature, it 
is presumable that they might serve as antigenic substances. It should 
be possible to prepare anti-amboceptor and anti-complement. As pre- 
viously mentioned, experiments have been reported which have been 
interpreted to indicate that it is possible to produce such immune anti- 
complements, but the evidence offered has not withstood criticism ; at 
the present time it is extremely unlikely that true anti-complements 
have been demonstrated. Anti-amboceptors were first produced by Ehr- 
lich and Morgenroth who injected as the antigen a hemolytic immune 
serum. If a hemolytic immune serum is injected in fairly large amounts 
into an animal for whose red cells the serum is specific, death results. 
By carefully-graded injections, however, it is possible so to immunize 
the animal that it becomes immune to the toxic effect of the serum. 
When so immunized the serum of this animal when added to a cell 
amboceptor mixture and incubated will prevent subsequent hemolysis 
on the addition of complement. Similarly anti-amboceptors may be 
produced by injecting serum containing amboceptors into other animals 
than those for which the serum is hemolytic. Ehrlich and Morgenroth 


were of the opinion that such anti-amboceptors represented an excess 
of cell receptors formed during the course of immunization and were 
thus free in the serum to combine with the cytophilic group of the 
amboceptor. Bordet found, however, that it was not necessary to use 
a hemolytic immune serum as an antigen and demonstrated an anti- 
amboceptor by injecting normal rabbit serum into guinea-pigs. The 
anti-serum formed in the guinea-pig not only neutralized hemolytic 
amboceptor of rabbit serum but other amboceptors of rabbit serum as 
well, and therefore it could not be regarded as combining with such 
a specific receptor as the cytophilic group of the amboceptor. This 
work was confirmed by several investigators, including Ehrlich and 
Sachs, who agreed with Bordet that the anti-amboceptor does not com- 
bine with the cytophilic group but offered the new assumption that the 
combination is with the complementophilic group. Muir and 
his co-workers have studied anti-amboceptors extensively and find 
no good ground for accepting the later interpretation of Ehrlich 
and Morgenroth. 

Muir offers an experiment as follows to illustrate the simple action 
of anti-amboceptor. Two tubes are marked A and B. Into each are 
placed one unit of cell suspension and three units hemolytic amboceptor 
(contained in rabbit serum), the mixture incubated and then washed 
and resuspended. To tube A is added 0.3 c.c. anti-amboceptor (pre- 
pared by injecting rabbit serum into guinea-pig), and to tube B is 
added 0.3 c.c. normal inactivated guinea-pig serum. The mixtures are 
again incubated and washed; to each tube is added one unit comple- 
ment and the tubes are again incubated. Hemolysis is complete in 
tube B but is absent or much inhibited in tube A, thus demonstrating 
the inhibiting effect of the anti-amboceptor. Such an anti-amboceptor 
as is here illustrated will operate only against amboceptors contained 
in rabbit serum. Similar amboceptors contained in goat serum would 
not be affected by the anti-amboceptor prepared by injecting rabbit 
serum into guinea-pigs. If in the preceding experiment the supernatant 
fluid were examined after the first incubation it would be found that 
the amboceptor had been absorbed; a fact also illustrated by the 
hemolysis in tube B. Even were anti-amboceptor and amboceptor 
mixed and then added to cells the amboceptor would not be prevented 
from absorption. If the supernatant fluid were taken after the last 
incubation complement would be found free in tube A but not in the 
full original amount, as can be shown by careful titration. The anti- 
amboceptor keeps a certain amount but not all the complement from 
being utilized. The converse, however, cannot be demonstrated, that 
is to say, complement cannot be shown to inhibit in any way the union 
of amboceptor and anti-amboceptor. Intricate experiments demon- 
strate, however, that the union of amboceptor and anti-amboceptor is 
loose and a certain amount of dissociation may occur upon the addi- 
tion of a normal serum homologous with the serum which contains 
the amboceptor. 

Anti-complements. As has been indicated above, it is improbable 


that any so-called anti-complements operate differently from these anti- 
amboceptors. Numerous substances and physical conditions are anti- 
complementary in that they destroy or inhibit the action of complement. 
These have been pointed out in discussing the nature of complement 
and must be considered in all experiments which utilize complement. 
It has been suggested that in the interaction between amboceptor and anti- 
amboceptor a precipitate is formed which fixes complement and that 
if such were the case the complement should not be recoverable. Muir 
has shown that it is possible to recover complement, as we have pointed 
out above. Nevertheless, even such a form of fixation may permit of 
dissociation, and, as we shall show in discussing complement fixation, 
there is much evidence in favor of the view that the action of these 
antilysins is dependent upon the fixing properties of precipitates. 

Physical Hemolysis. Hemolysis is produced not only by the 
serum components discussed in the preceding paragraphs but also by 
chemical and physical agents, by bacterial products, by certain vegetable 
poisons and by venoms. Studies of these forms of hemolysis are of 
interest not only because of their intrinsic value but also because they 
serve to throw some light on serum hemolysis. 

The necessity for using an isotonic salt solution for the preservation 
of erythrocytes is well known and equally well known is the fact that 
reduction of salt content of the menstruum beyond a certain point leads 
to solution of hemoglobin, which in distilled water is seen as complete 
hemolysis. This is not merely a question of solubility of hemoglobin 
for this substance is soluble in physiological salt solution to the same 
degree as in distilled water. For the same reason it is not a matter 
of simple osmosis of the hemoglobin. Although distilled water pro- 
duces swelling of the cells before the solution of hemoglobin the 
rupture of the cell is of no especial importance for cells may be cut 
into pieces in physiological salt solution without hemolysis appearing. 
From experiments of Fischer it would appear that the hemoglobin is 
held in combination with the stroma by adsorption and that the action 
of the water causes a physical separation. By combining fibrin, a 
hydrophyllic solid colloid, with carmine, a hydrophobic colloid dye, 
Fischer was able to produce phenomena closely resembling hemolysis. 

Fragility of Erythrocytes. The corpuscles of different animals 
differ in the point to which reduction in salt concentration of the sur- 
rounding menstruum leads to hemolysis. This is spoken of as a differ- 
ence in resistance to hypotonic salt solution or a difference in fragility. 
There may be a very slight difference in fragility of the corpuscles of 
different individuals of the same species and diseased conditions may 
lead to well-marked alterations. In man a simple secondary anemia may 
lead to a normal or reduced fragility, whereas pernicious anemia leads to 
increased fragility. Obstructive jaundice is accompanied by decreased 
fragility, whereas familial hemolytic jaundice shows increased fragility. 
In the anemia of animals following removal of the spleen there is a 
decrease of fragility or, in other words, an increase of resistance to 
hypotonic salt solutions and also to other hemolytic agents. 


Hemolysis may be caused by other physical agents, such as 
freezing (particularly when followed by thawing), heat of 62 to 64 C. 
in the case of mammalian corpuscles or slightly less in the case of 
cold-blooded animals and, as Rous has shown, by shaking. 

Chemical Hemolysis. The influence of chemicals on hemolysis 
appears to be a factor of their permeation of the stroma. Wells states 
that there seem to be two types of permeating substances, one such as 
urea, which does not act in isotonic solutions of sodium chloride, and 
the other such as ammonium chloride, which acts either in isotonic or 
non-isotonic solutions. Hamburger, as quoted by Wells, states that 
erythrocytes in relation to organic substances are (a) impermeable 
for sugars, including cane sugar, dextrose, lactose, arabinose and man- 
nose; (&) permeable for alcohols in inverse proportion to the number 
of hydroxyl groups they contain, also for aldehydes (except paralde- 
hyde), ketones, ethers, esters, antipyrin, amides, urea, urethan, bile 
acids and their salts; (c) slightly permeable for neutral amino-acids, 
such as glycocoll and asparagin. In relation to inorganic substances, not 
including the salts of fixed alkalis, the erythrocytes are (a) " imperme- 
able for the cations Ca, Sr, Ba, Mg, and (&) permeable for NH 4 ions, 
for free acids and alkalis." It will be noted that certain of the organic 
substances for which the cells are permeable are solvents of lipoids, 
particularly those lipoids of the stroma, cholesterol and lecithin, a 
phenomenon which will be referred to again in discussing venom 
hemolysis. Other chemical hemolysins include veratrin, digitalin, 
arseniuretted hydrogen (in the body but not in the test tube), nitro- 
benzol (important in denatured alcohol poisoning), nitrites, guaiacol, 
pyrogallol, aniline compounds, alcoholic extracts of tissues and products 
of tissue autolysis. Salt solution extracts of various organs are 
hemolytic and have been called organ hemolysins. These bodies 
resist boiling, do not act as antigens, hemolyze at 37 but not at o C., 
are not increased in activity by complement but are inhibited by the 
presence of serum. Noguchi has studied alcoholic tissue extracts ex- 
tensively and finds them also hemolytic. He has come to the con- 
clusion that the active elements in organ hemolysis are soaps. 

Bacterial Hemolysins. Bacteria may by their growth lead to suf- 
ficient acid or base formation in the media as to make the latter 
hemolytic. Of equal importance is the fact that certain bacteria may 
produce hemolytic bodies not of definitely acid or alkaline character, 
called bacterial hemotoxins. These substances include for the most 
part the products of pathogenic organisms, such as tetanolysin, 
staphylolysin, streptolysin, typholysin, vibriolysin (El Tor strain of 
cholera), anthrax-lysin and certain other less important forms. Certain 
saprophytes also are capable of producing lysins, as for example mega- 
theriolysin, proteus-lysin and the lysin of bacillus Welchii and others 
of the gas gangrene group. An important bacterial hemotoxin is that 
of bacillus pyocyaneus. The exact nature of these substances is not 
known, but Burckhardt has shown that staphylolysin is dialyzable, 
thermolabile, ether soluble and does not give protein or biuret reactions. 


The action on the cells is independent of complement, there is no com- 
bination at o C, but at 6 C. combination occurs, leading to hemolysis 
only at higher temperatures. It, therefore, seems likely that these 
bodies are similar to /toxins with a special affinity for erythrocytes. 
The most favorable medium for developing these hemotoxins is broth, 
but individual organisms require special conditions in the broth for 
maximal production of hemotoxin. The development of the toxin fol- 
lows fairly definite curves for the different organisms. For example, 
staphylolysin begins to appear on the third day, reaches a peak on the 
fifth day, drops on the sixth day, rises again on the eighth day, drops 
again and reaches a final maximum on the thirteenth day. Megatheri- 
olysin reaches a maximum on the seventh day and almost disappears 
by the fifteenth day. De Kruif has recently shown that streptolysin 
reaches its maximum in a few hours and has almost disappeared by 
the end of twenty-four hours. The action is variable for different 
species of corpuscles; staphylolysin acts powerfully on horse, sheep 
and other bloods but only slightly on human and goat blood, whereas 
megatheriolysin acts powerfully on human blood but not at all on horse 
'blood. Nakayama has studied the streptolysin and finds that it is 
filterable. He also passed the organisms through two species of 
animals and finds that after animal passage the streptolysin is more 
actively lytic for the corpuscles of the species which last harbored the 
organisms. Streptolysin unites with the corpuscles in the course of 
hemolysis, but the filtrate, after absorption of lysin, remains toxic for 
mice. Many of the bacterial hemotoxins are thermolabile, being de- 
stroyed at 60 to 65 C., but others are resistant to temperatures as 
high as 1 00 C. The bacterial hemotoxins are active in vivo as well 
as in vitro and are capable of producing severe anemias and even 
death. An intravenous dose of 2.0 c.c. of a ten-day-old filtered broth 
culture of staphylococcus produces in the rabbit marked reduction in 
hemoglobin and the number of erythrocytes and may cause death in 
six or seven days. It is probable that the secondary anemias which 
often follow attacks of acute infectious disease may be dependent upon 
bacterial hemotoxins. Ford, Lawrence and Williams have found that 
cultivation of the bacillus Welchii in milk leads to the formation of 
bacterial hemolysins, thus disproving the opinion previously held 
that the hemolysis in gas bacillus infection was due to the formation 
of lactic or butyric acid. The hemolysin described by Ford and Law- 
rence is relatively stabile, not being destroyed until a temperature of 
62 or 63 C. has been reached. It has other characters of true toxin 
in that it is digested by pepsin and hydrochloric acid as well as by 
pancreatin. It is precipitated by ethyl alcohol. It is antigenic, and 
these investigators found that they could, by immunization, produce an 
anti-hemolysin or anti-hemotoxin in titers of i 1000, 1-1250. 

Vegetable Hemolysins. Among the hemolytic substances of 
vegetable origin are to be included those already discussed as phyto- 
toxins, namely ricin, abrin, crotin, robin, phallin. Crotin and phallin 
are more markedly hemolytic than the others, which are rather hemag- 


glutinative than hemolytic. The phytotoxins resemble some of the 
bacterial hemotoxins in that they may serve as antigens for the .pro- 
duction of antitoxins but differ in that, as a rule, they are thermostable. 
Both groups act according to the law of multiple proportions. Of 
considerable importance from the experimental point of view are the 
saponins " a closely related group of glucosides found in at least 
forty-six different families of plants" (Wells). They are thermo- 
stable, do not act as antigens, have a fairly definite chemical composi- 
tion and are in these particulars to be separated from true toxins. They 
operate injuriously not only upon the erythrocytes but also on other 
body cells, especially those of the central nervous system. Cholesterol 
and lecithin both combine with saponin, the former in such a way as 
to prevent hemolysis. Therefore, it is assumed that the hemolytic 
action of saponin is dependent upon its action on the stroma lipoids. 
Normal serum is anti-hemolytic for some of the saponins, a property 
which may be slightly increased by careful immunization ; Kobert be- 
lieves this increase to be due to an increase of blood cholesterol. 

Venom Hemolysins. The venom hemolysins or hemotoxins are 
found in different amounts in all venoms, and the phenomenon of venom 
lysis is of considerable importance not only because of its scientific 
interest but also because of its employment in certain clinical tests. 
The venoms possess not only lytic but also hemagglutinative properties, 
the two usually being present in inverse ratio. Flexner and Noguchi 
demonstrated that the lysin of venoms requires activation by some 
substance which exercises a complementary power. They found that 
cobra hemotoxin dissolves the red corpuscles of certain animals (ox, 
sheep and goat) only in the presence of serum, but that it may dis- 
solve other erythrocytes (dog, guinea-pig, man, rabbit, horse) in the 
absence of serum. This difference is probably due to a content of 
activator in the latter cells, which activator must be furnished by serum 
for the lysis of the former cells. Kyes found that he could extract 
an activator from those cells which do not require serum for venom 
lysis but was unable to do so in the case of those cells which require 
serum activation. This activating substance was found to be ether 
soluble. Kyes subsequently found that lecithin can activate venoms and 
assumed that this lipoid constituted the bulk of the activating sub- 
stance. The substance in serum is usually active only after the serum 
has been heated, but with some sera heating is not necessary. Kyes 
and Sachs believed this to be due to differences in the nature of the 
lecithin union in the serum. Kyes mixed cobra poison with a chloro- 
form solution of lecithin and obtained a substance which he named 
cobra lecithid capable of activating cobra venom. Von Dungern and 
Coca, upon investigating the subject, came to the conclusion that the 
cobra venom contains a ferment capable of splitting the lecithin so 
as to yield certain substances such as oleic acid and that the resulting 
hemolysis is due to the activity of these secondary substances. Noguchi 
holds that although lecithin exists in the stroma of red blood-cells it 
is not present in a form available for venom activation and that the 


degree of susceptibility to hemolysis depends upon the amount of such 
ether soluble activators as fatty acids (particularly oleic acid) and 
their soluble soaps. He regards fatty acids, neutral fats and soluble 
soaps as endocellular complement and assumes certain similarities with 
serum complement. Certain soap serum mixtures were found to be 
capable of completing an amboceptor cell mixture but numerous objec- 
tions have been interposed against both the fact and the interpretation 
so that at the present time there is no good ground for believing that 
the activator of cobra lysin is a true complement or that Noguchi's soap 
mixtures are comparable to serum complement. If the activator cannot 
be regarded as complement, the venom lysin cannot be looked upon 
as an amboceptor, for it shows no specificity and does not require 
serum complement for activation. Kyes in a recent publication 
gives what may be regarded as the modern view in regard to venom 
lysis as follows: 

" i. There is present in all venoms a hemolysin existing as one of 
a number of distinct toxins. 

" 2. This hemotoxin effects hemolysis only in conjunction with 
a so-called complementing substance which, however, may be found 
within the erythrocytes. 

" 3. The reaction between the hemotoxin and lecithin is essentially 
a chemical reaction resulting in the formation of a complete lysin. 

" 4. This complete lysin is a true toxin in that it stimulates the 
production of a specific antibody." 

Although the experiments of Zunz and Gyorgy are not to be re- 
garded as indicating that they have found other activating substances 
for cobra venom hemolysis, nevertheless, they have determined that 
hemolytic activity of cobra venom is increased by certain compounds of 
protein destruction, including certain albumoses and amino-acids. 

The hemolytic property of cobra venom has served as a basis for 
proposed clinical tests. Calmette noted that in tuberculosis the blood 
contains more than the usual amount of lecithin and that small amounts 
of serum of such patients served to activate cobra venom lysin. The 
test is not positive in more than 78 per cent, of tuberculous patients and, 
furthermore, is by no means specific. Similar increases of lipoid con- 
tent of serum have been found in certain diseases of the central nervous 
system, a fact leading to the Much and Holzmann psycho-reaction, 
which also is not specific. Weil has maintained that in syphilis the 
corpuscles are more resistant to venom hemolysis than is normal, 
except in the earlier stages where the corpuscles are said to be hyper- 
sensitive. As time has passed the suggested clinical tests have not 
come into general use largely because of lack of specificity. Un- 
doubtedly the blood exhibits alterations in lipoid content at different 
times in various diseases, and in all probability there is a parallel altera- 
tion in its power to activate venom lysin, but no one disease shows this 
change exclusively or even constantly. 

Cytotoxins. Specificity. As erythrocytes may act as antigenic 
substance, so may other body cells. The antibodies produced by injec- 


tion of these latter cells were called cytotoxins by Metchnikoff, and 
the name has been retained in spite of the fact that the immune bodies 
are not toxins in the strict sense of the word but are amboceptors 
similar to the hemolytic amboceptors. It was thought that cytotoxins 
might be strictly specific for the antigenic cells of different organs 
within the same species, but more thorough investigation has shown 
that such " organ specificity " is not demonstrable. Hemolysins, for 
example, are lytic for other body cells, such as liver and kidney, pro- 
vided these cells are of the same species. Hepatolysins and nephrolysins 
are also active as hemolysins within the species. In other words, 
these antibodies are species specific but not organ specific. It may be 
true that a cytotoxin acts more especially on its antigenic organ cells 
than upon other cells, as is maintained by Pearce for the nephrolysins, 
but the action is not exclusively upon the antigenic cells. In an ex- 
tensive study Pearce, Karsner and Eisenbrey were unable to demon- 
strate any strict " organ specificity " by means of cytolysis, precipitation, 
agglutination or the anaphylaxis reaction. In this work the organs were 
washed by perfusion with large amounts of salt solution and thus pre- 
pared for injection. Bell has pointed out that even the most careful 
perfusion will not entirely remove the blood from organs and therefore 
a certain amount of blood must be injected with the other cellular 
antigen. Nevertheless, the early work of Landsteiner, MetchnikofT and 
of Moxter showed that spermatozoa which can be obtained free from 
blood may lead to a spermatolysin which also acts as a hemolysin. The 
amount of blood injected with carefully- washed organs is so small 
that it can have but little antigenic power, too little to be consistent with 
the well-marked hemolytic power of the cytotoxic sera. Recently, 
however, Wilson and Oliver have absorbed the hemolysin from cyto- 
toxic sera by means of erythrocytes and maintain that there is a very 
definite organ specific cytotoxin contained in nephrolytic serum pre- 
pared by immunizing with kidney substance. This specific nephrolysin 
can be removed by absorption with kidney substance but not with other 
organs. If these studies are extended and confirmed, much new light 
may be thrown on the subject of organ specificity. 

In spite of the apparent lack of strict organ specificity, the cytotoxins 
of certain types of cells deserve mention, namely those resulting from 
the injection of leucocytes and of crystalline lens. Following a brief 
communication by Delezenne concerning leucotoxins, Metchnikoff 
studied the matter by injecting guinea-pigs with material from the 
mesenteric lymph-nodes and from the bone marrow of rabbits. The 
resulting immune serum was highly toxic for guinea-pigs, but if given 
in sufficiently small doses produced first a marked leucopenia, fol- 
lowed in several days by a leucocytosis. This was confirmed by others 
who used for injection also leucocyte emulsion, and although species 
specificity was strict, the cellular specificity was not. Lucatello and 
Malon were able to obtain a serum by the use of leucocytes from cases 
of leucemia and treated a series of cases with this serum. The leuco- 
cytes were reduced in number and the spleen diminished in size, but 


there was no permanent improvement. The lack of cellular specificity 
in such sera is an a priori argument against their use. 

Lens Cytotoxin. The injection of crystalline lens leads to the 
formation of a cytolysin which is organ specific but not species specific, 
similar to the production of precipitins by lens protein. Such a cyto- 
toxin prepared by the use of the crystalline lens of the dog is specific 
for all mammals, birds and fish and will not act upon other cells from 
these animals. The fact that the injection of lens into animals of the 
same species or even into the same individual leads to the production 
of isocytotoxins and autocytotoxins led Romer to build up a theory 
concerning the origin of cataract. He suggested that the constant 
absorption of lens protein from the normal process of tissue wear and 
tear leads to the development of an isocytotoxin which in later life 
produces the degeneration of the lens seen in cataract. If such were 
the case cataract should be a much more frequent complication of age 
than it is and the lens should be a soft pulpy organ as the result of cyto- 
lysis. Furthermore, complement is not available in the fluids of the eye 
and the cytolytic amboceptor is not to be completed in that position. 
Other theories as to the etiology of cataract are so much more logical 
that Romer's hypothesis has been practically abandoned. 

Aside from the foregoing example of isocytotoxin and autocytotoxin 
formation, there are no well-determined illustrations of this phenomenon 
except for the demonstration by Metchnikoff of isospermatotoxins. 

Bacteriolysins. The death and solution of bacteria in the processes 
of resistance to disease may be accomplished by the activity of phago- 
cytic body cells or by virtue of properties of the blood and body fluids 
similar in every way to those properties which lead to hemolysis. In- 
deed, the discovery of bacteriolysis antedated that of hemolysis even to 
the point of understanding the essentials of its mechanism. Nuttall 
in 1888 demonstrated that fresh normal defibrinated blood has the 
power of killing bacteria. He set up a series of tubes, each containing 
the same amount (0.5 to i.o c.c. defibrinated blood) and added to each 
a small platinum loopful of material from the spleen of a mouse previ- 
ously inoculated with anthrax. These tubes were incubated and at differ- 
ent time intervals gelatin plates were made from the tubes and a control 
made from the splenic material. This showed that as incubation pro- 
ceeded the bactericidal activity of the blood became apparent. Buch- 
ner confirmed this fact in 1889 with a slightly different method, 
whereby a larger amount of blood and bacteria were mixed in one 
container and incubated and small standard amounts withdrawn by 
pipette and plated. It was found that if the blood were heated or 
allowed to stand, its bactericidal power was lost and Buchner named 
the thermolabile element alexin. He believed it to be of the nature 
of a ferment, suggested that it might originate in body cells, possibly 
leucocytes, and recognized the fact that it is not specific. 

The Pfeiff er Phenomenon. The next important advance appeared 
in the studies of Pfeiffer and his co-workers, who, in 1893, 1894 and 
subsequently, published the details of what we now speak of as the 

FIG. 15. Stages in lysis of cholera vibrios, 
showing the reduction to large coccoid 
forms before final solution. (Modified 
from Pfeiffer and Friedberger, Lehrbuch 
der Mikrobiologie, Jena, 1919). 


Pfeiffer phenomenon. These discoveries were incident to the investi- 
gation of immunity to cholera spirilla. The method is essentially that 
of studying the changes taking place in the spirilla following intraperi- 
toneal injection in guinea-pigs. If the guinea-pig had survived preceding 
inoculations and had thereby developed immunity the injection of or- 
ganisms was followed by loss of their motility, transformation into 
oval translucent granules and finally disappearance of the bacteria with 
complete recovery of the animal. If the spirilla were of only low 
degree of virulence the same phenomenon could be observed in a 
normal animal, but if the animal were highly immune it could survive 
doses of virulent organisms much greater than those fatal for normal 
guinea-pigs. It was found that the simultaneous intraperitoneal injec- 
tion of serum from an immune pig and of spirilla into a normal pig 
served to protect the animal and that this protection could be conferred 
as well by heated as by non-heated immune serum. The mechanism in 
all cases was the same and not dependent upon phagocytic activity. 
Furthermore, the protection was found to be specific. Pfeiffer was 
unable to demonstrate the phenomenon in vitro (hanging drop prepara- 
tion) and therefore assumed that some substance provided by the peri- 
toneal endothelium served to activate the bacteriolytic process. 

In the demonstration of the Pfeiffer phenomenon it is necessary to have 
a series of fairly young guinea-pigs of about 200 grams in weight and a culture 
of cholera spirilla whose virulence is well established, because the virulence of 
the organisms plays quite as important a part as their number. The immune 
serum may be produced in the rabbit, goat or other animal by repeated inocula- 
tion with the organisms. The organisms may be injected in measured volumes 
of broth cultures or of saline suspensions of agar cultures ; they may also be 
measured by weight by the use of a standard platinum loop which takes up 
approximately 0.002 gm. organisms. The immune serum is diluted as indicated 
in the following protocol and the bacteria and serum are injected simultaneously. 
Peritoneal fluid is withdrawn at intervals of 10, 20, 30, 45, 60 minutes, the 
intervals being altered as circumstances indicate. The withdrawal is by means 
of drawn out capillary pipettes introduced into the belly cavity through a 
small incision in the skin. The material may be examined in a hanging drop or 
may be spread and stained by the ordinary bacterial dyes. A protocol from 
Pfeiffer's own work follows : 

Weight of 
in grams 






Dose of Dose of 

spirilla immune Examination of 

in grams serum in c.c. Result peritoneal fluid 

0.002 0.05 Lives After 15 minutes, only gran- 

ules present. 

0.002 0.02 Lives After 20 minutes, only gran- 

ules present. 

0.002 0.006 Lives Sterile after 35 minutes. 

0.002 0.003 Lives After 25 minutes, numerous 

granules, isolated, non- 
motile spirilla. After i 
hour practically sterile. 

0.002 o.ooi Died during After 25 and 50 minutes, 

night numerous granules but 

also numerous active spir- 
illa. After loo minutes, 
only active spirilla. 





Weight of 
in grams 


Dose of 


in grams 


Dose of 


serum in c.c. 




O.2 C.C. 

serum as 

Examination of 
Result peritoneal fluid 

Died during After 25 minutes, a few 
night granules, numerous active 

spirilla. Progressive in- 
crease of spirilla. 

Died during After 25 minutes, few gran- 
night ules, numerous active 
spirilla. Autopsy after 
several hours showed pus 
on the liver, numerous 
spirilla mostly free in exu- 
date, with granules both 
free and within cells. 

In the foregoing experiment it is seen that 0.003 c.c. immune serum 
serves to protect a guinea-pig of about 200 grams from an otherwise 
fatal dose of cholera spirilla. Pf eifFer used this method to titrate bac- 
teriolytic sera and in this case would have indicated the serum as 
containing in each cubic centimeter 333 immune units. 

Bacteriolysis in Vitro. Further study of the phenomenon more 
particularly by Metchnikoff and by Bordet led to the discovery that the 
process may be demonstrated in vitro, in spite of Pf eiffer's failure to do 
so. Metchnikoff was able to produce lysis of spirilla in hanging drop 
preparations by adding to the mixture of spirilla and immune serum an 
extract of leucocytes, thus offering evidence in favor of the influence 
of leucocytes in destruction of bacteria. Bordet demonstrated that 
although the activity of the immune serum is destroyed by heat of 
50 C. to 60 C., the serum may be rendered active again by the addi- 
tion of a small amount of fresh serum, an amount of fresh serum in 
itself incapable of producing bacteriolysis. He found that the speci- 
ficity of the immune serum resides in a substance which he later named 
the sensitizer (the Ehrlich amboceptor). The alexin of Buchner 
(complement) was found to exhibit no specificity and was not increased 
by immunization. In the course of these studies Bordet found that 
the corpuscles in the fresh normal guinea-pig serum were agglutinated 
by the immune goat serum and that the spirilla were often likewise 
agglutinated. Suspecting that if both blood-cells and bacteria are 
agglutinable, the blood-cells might be the subjects of lysis as well as 
are bacteria, Bordet was led to the discovery of the phenomenon of 
hemolysis. The studies of Toitsu, Matsunami and Kolmer would indi- 
cate that all bacteriolysis is not necessarily dependent upon the activity 
of complement, for they found that anti-meningitis sera which were 
freed from complement possessed bactericidal properties. Ecker has 
made similar observations in regard to a serum specifically bacteriolytic 
for the diphtheria bacillus. Nevertheless, Ecker found that the addi- 
tion of complement increases the bacteriolytic action of this serum. 

The Pfeiffer phenomenon was found applicable to bacteria other 
than the cholera spirilla, including particularly the typhoid bacillus, 
paratyphoid, dysentery and colon bacillus. With these organisms the 
phenomenon proceeds more slowly than with cholera spirilla. Were 



no simpler means available, the Pfeiffer phenomenon might well serve 
as a laboratory method of identifying cultures of the bacteria. 

Wright's Method for Bacteriolysis. In the course of subsequent 
studies, other methods of investigation of bacteriolysis have been de- 
vised, those of Wright, of Neisser and Wechsberg and of Buxton de- 
serving especial mention. Wright exercised his usual ingenuity in 
attacking this problem and devised two methods, one by dilution of 
serum and the other by dilution of the culture of organisms. For the 
collection of serum he used the Wright pipette such as is employed 
for determining opsonic content of serum. The serum was diluted 
with different amounts of bouillon. The culture was mixed with 
melted gelatine and to measured amounts of this, mixture was added 
the proper amount of serum dilution. The final mixtures were incu- 
bated in capillary pipettes for two to three days at 22 C, then placed 
under low magnification of the microscope and the number of colonies 
-in the pipettes determined. In the second method the culture was 
diluted in varying amounts of broth by means of a specially con- 
structed capillary pipette and the suspension blown into a watch glass. 
The culture dilutions were mixed with a standard amount of serum 
and incubated in special pipettes. If the serum was insufficient to kill 
all the organisms, there was bacterial growth, and the medium became 
cloudy. Having, by previous plating, determined the number of organ- 
isms in a given bulk of broth culture, it was possible to determine how 
many organisms could be killed by the standard amount of serum. 
The outlines of these methods are given because of the ingenuity dis- 
played and the exact information gained, although at the present time 
they are not extensively employed. 

The Neisser- Wechsberg Phenomenon. The Neisser and Wechs- 
berg method was described almost contemporaneously with that of 
Wright. They mixed inactivated serum dilutions in test tubes with 
either broth cultures or salt solution suspensions of organisms, added 
complement and incubated. Definite amounts of these mixtures were 
added to melted solid culture media, such as agar, and plates poured. 
After incubation of the plates, the colonies were counted and the bacte- 
riolytic activity of the serum thus determined. A protocol taken from 
the studies of Neisser and Wechsberg will serve to illustrate the method. 







of culture 

immune serum 

1/5000 c.c. of a 24- 
hour broth culture 
of vibrio Metchnikovi 

Fresh guinea- 
pig serum 

I.O C.C. 

0.3 c.c. 

0.5 c.c. 

0.3 c.c. 

0.25 c.c. 

0.3 c.c. 

O.I C.C. 

0.3 c.c. 

0.05 c.c. 

0.3 c.c. 

0.025 c.c. 

0.3 c.c. 

O.OI C.C. 

0.3 c.c. 

0.005 c.c. 

0.3 c.c. 

0.0025 c.c. 

0.3 c.c. 

0.00 1 C.C. 

0.3 c.c. 

0.0005 c.c. 

03 c.c. 

Number of colonies 
on plates 

Many thousands 
Many thousands 
Many thousands 
Few hundred 
About 100 
About 50 
About 100 
Many thousands 
Many thousands 



_ Amount Inactivated Fresh guinea- Number of colonies 

Controls o f culture immune serum pig serum on plates 

1 1/5000 c.c. ... ... Many thousands 

2 1/5000 c.c. o.oi c.c. . . . Many thousands 

3 0.01 c.c. . . . None 

4 1/5000 c.c. ... 0.3 c.c. Many thousands 

5 ... i.o c.c. None 

The broth culture is so diluted that 0.5 c.c. are added to each tube. All tubes 
are made up to constant volume with 0.85 per cent, salt solution. Incubation is 
for three hours at 37 C, after which five drops from each tube are added to 
a tube of melted agar for plating. 

The Neisser-Wechsberg method not only presents a means of work- 
ing with bactericidal sera but also demonstrates both the necessity for 
the presence of complement to complete the bactericidal amboceptor 
and the appearance of inhibition zones in the stronger concentra- 
tions of the immune serum. Neisser and Wechsberg interpreted the 
inhibition zone as illustrating what they called " complement devia- 
tion," a term frequently used incorrectly as synonymous with com- 
plement fixation. They believed that if an excess of amboceptor units 
is present, a certain number of these units will combine with the avail- 
able complement units, thus leaving a number of amboceptor units 
unsaturated with complement. The amboceptor is present in amounts 
too large to be entirely absorbed by the antigenic bacteria and therefore 
it is assumed that a certain number of the free amboceptor units 
combine with a number of complement units, thus preventing a suf- 
ficient amount of complement to combine with the amboceptor units 
already absorbed by the bacteria for the process of bacteriolysis. In 
tubes four to nine of the preceding protocol the amboceptor units and 
bacteria are closely enough balanced to ensure complete absorption 
of amboceptor and thus permit of full action of complement ; there 
being no free amboceptor, there is no " deviation " of complement. 
Except for the possible evidence afforded by the Ehrlich and Sachs 
experiment (see page 125) there is no other experimental evidence sup- 
porting the view that free amboceptor may enter into combination 
with complement. Gay has suggested that the inhibition may be due to 
precipitation by the interaction of the immune serum and bacterial 
protein which may have gone into solution, the precipitate operating 
to fix complement and prevent its combination with bacteriolytic am- 
boceptor. Whilst precipitation may undoubtedly be of significance in 
this connection, we are of the opinion that the resemblance to col- 
loidal reactions as described in connection with precipitation and agglu- 
tination, wherein excess of one colloid may prevent the occurrence of 
precipitation or flocculation, offers an equally satisfactory explanation 
;for the Neisser-Wechsberg phenomenon and that we are therefore 
justified in regarding the reaction as illustrating " inhibition zones " 
where the concentration of amboceptor is great. The failure of bac- 
teriolysis in tubes eleven and twelve is due, of course, to insufficient 
amount of amboceptor. The control tubes show that neither ambo- 
ceptor nor complement alone is capable of producing bacteriolysis. 

Buxton's Method for Bacteriolysis. Buxton determined that 


active immune serum shows the same inhibition zones and also simplified 
the method. By allowing the original tubes to incubate twenty-four 
hours at 37 C, the degree of clouding of the medium by bacterial 
growth gives an excellent indication of the degree of bacteriolysis. He 
found that normal rabbit serum shows bacteriolytic powers in strong 
concentration, gradually diminishing as dilution proceeds. Thus the 
low titer normal amboceptor fails to show inhibition zones, as is true 
of low titer agglutinins and precipitins. A protocol from Buxton's 
work shows the difference in activity of normal serum and immune 
serum as well as the correspondence between the results of plating and 
observation of original tubes. 


Dilution Count of colonies on plates Observation of original tubes 

of sera Normal serum Immune serum Normal serum Immune serum 

i o Many thousand Clear Cloudy 

1-2 o Many thousand Clear Cloudy 

1-5 2 Many thousand Clear Clear 

1-20 2500 4-5000 Cloudy Clear 

1-40 Many thousand 4-5000 Cloudy Clear 

1-80 Many thousand Many thousand Cloudy Cloudy 

i-ioo Many thousand Many thousand Cloudy Cloudy 

Teague and McWilliams have confirmed the work of Buxton and 
others showing that normal rabbit serum is capable of killing large 
numbers of typhoid and paratyphoid bacilli, but that the sera of rabbits 
highly immunized against these organisms do not kill these bacilli. 
These investigators have emphasized further that the normal bacteri- 
olytic activity of rabbit serum for typhoid and paratyphoid bacilli is 
not materially altered by immunization. In human typhoid fever the 
blood serum normally shows bacteriolytic activity, but in spite of this bac- 
teria multiply in the tissues apparently because the lymph does not pos- 
sess bacteriolytic powers. Stone more recently made similar observations 
but found further that fresh immune typhoid serum in vivo has appar- 
ently a high bactericidal power, while fresh normal serum in vivo 
has no protective power. Typhoid bacilli disappear more quickly from 
the organs of immune animals than from normal animals, but macerated 
organs from immune animals, cut sections, or their extracts are not 
bactericidal even on the addition of fresh immune serum. This work 
indicates that the destruction of typhoid bacilli in the immune animal 
is due to some interaction between the tissue cells and plasma in vivo 
or other unknown factor. 

The Bioscopic Method for Bacteriolysis. Neisser and Wechsberg 
also devised the so-called bioscopic method of studying bacteriolysis. 
They took advantage of the fact that living cells possess the power of 
converting methylene blue into its colorless leucobase. By careful 
adjustment of the number of bacteria it was possible to mix the various 
agents together, add a very dilute alcoholic solution of methylene blue, 
cover with paraffin and incubate. The degree of decolorization indi- 
cates the relative amount of bacterial growth. 

Summary of Cytolysis. In summary it may be said that the phe- 


nomenon of cytolysis represents a general biological phenomenon ap- 
plicable to vegetable cells, exemplified by bacteria, and also to a wide 
variety of animal cells. In both kingdoms there is a marked species 
specificity exhibiting, as do other immune processes, the phenomenon 
of group reactions. In so far as bacteriolysis is concerned, inhibition 
zones appear, apparently similar to the inhibition zones of precipitation 
and agglutination. Two bodies interact to produce cytolysis, a ther- 
mostable body, the amboceptor or sensitizer, which may be increased 
by immunization, and a thermolabile body, the complement or alexin, 
which does not react to immunization. The amboceptor appears to 
act by preparing the antigenic cells for the lytic action of the com- 
plement rather than by furnishing a two-armed link between cell and 
complement. The reaction takes place more nearly according to the 
physical chemical laws of colloidal reactions than the simpler laws of 
reactions between inorganic chemicals. The protection afforded an 
animal which possesses bacteriolytic immune bodies is obvious, and 
the role these bodies play in natural and acquired immunity to disease 
must be of great importance. 

















Introduction. Metchnikoff has defined the phagocyte as a cell 
capable of ingesting foreign bodies. Similarly the process of phago- 
cytosis can be referred to as the process of ingestion of foreign bodies 
by a cell. In the study of unicellular organisms and of certain lower 
forms of multicellular organisms it has been found that the process 
of phagocytosis is an important means of obtaining nutrition. That 
such a simple process could have any bearing on the resistance of 
vertebrates to disease was not pointed out for many years. The very 
earliest study of bacteriology and immunity led to the knowledge of the 
fact that the injection of bacteria into animals led, under favorable 
conditions, to the disappearance of these bacteria. The investigation 
of the cause of this disappearance resulted first in the belief that it was 
due to solution of the bacteria by body fluids, more especially the blood. 
Certain early investigators had noticed that following such injections 
of bacteria the bacteria might appear within tissue cells, but Panum 



was the first to interpret the phenomenon in an immunological sense. 
He pointed out that the penetration of bacteria into living cells, as 
previously maintained by Birch-Hirschfeld, probably had much to do 
with the disappearance of bacteria following injection. Subsequently, 
it was shown that bacteria do not penetrate into cells but rather are 
taken up by the cells. This work of Panum did not lead to any direct 
result in the study of immunology, for Metchnikoff in his early work 
on the subject was ignorant of it. Roser had also stated that according 
to his opinion the immunity of healthy animals and plants against in- 
fectious organisms rests upon (a) the relative salt content of their 
fluids and (b) the capacity of their contractile cells to take up the 
invading organisms. Roser, however, did not support this statement in 
later studies, and again Metchnikoff was ignorant of this work when 
he took up his great work on phagocytosis. Metchnikoff had studied 
extensively the nutrition of certain of the lower forms of animal and 
vegetable life and also their defenses against the invasion of harmful 
parasites. From this work he was led to the conclusion that the defense 
of higher animals depends in great part upon the phenomenon of 
phagocytosis. This statement was magnified into a conflict between 
the so-called cellular theories of immunity and the humoral theories 
of immunity. At the present time, however, such a conflict does not 
exist because the two theories of immunity are in perfect harmony with 
one another, and it is known that they are dependency interrelated. 

The process of phagocytosis involves three steps; first, the ap- 
proach of the cell and the material to be taken up ; second, the ingestion 
of the material, and, third, the destruction of such material as may be 
dissolved by the digestive fluids of the cell. The problem of the 
approach of the cell and material to be ingested is one fundamentally 
of irritability. The irritability of living tissue is in response to certain 
stimuli and such stimuli include chemical, thermal, osmotic, photic, 
mechanical and other physical agents. In the early studies of the 
physiology of stimulation the response of a cell to a stimulus was 
believed to be governed by the Weber-Fechner law, which states that 
the intensity of sensation varies with the logarithm of the intensity 
of the stimulus or, in other words, as the stimulus increases by geometric 
progression the response increases by arithmetical progression. This 
law has been found by further study to be untenable, for it has been 
shown that logarithmic functions are not applicable to very strong 
stimuli. In phagocytosis chemical stimuli are the most important, and 
the response to such stimuli is referred to as chemotaxis. 

Mutual Approach (Chemotaxis). Chemotaxis may be positive or 
negative, according to whether it attracts the two bodies or repels them. 
Such attraction or repulsion does not depend essentially on the acidity 
or alkalinity of the medium but does depend in certain measure upon 
its concentration. Not only does variability of concentration play a 
part, but the adaptability of the cell itself is of importance ; for example, 
myxomycetes plasmodia exhibit negative chemotaxis in the presence 
of sugar in certain concentrations, but after the organism becomes 


accustomed to the presence of the sugar a positive chemotaxis appears. 
The lower animal and vegetable cells exhibit a certain amount of selec- 
tion in the material which they take up, and the leucocytes of higher 
organisms may in a similar manner exhibit selectiveness. According 
to our present-day physical conception of the activity of living proto- 
plasm, this selectiveness would depend in all probability upon varying 
sensibility to chemotactic influences or variation in the intensity of the 
chemotactic stimuli. 

Ingestion of Foreign Body. The actual ingestion of the foreign 
body depends upon the motility of the cell protoplasm, and this motility, 
of course, is a function of the irritability of the protoplasm. Such 
motility determines the ameboid movement of the cell to the material 
to be ingested. Having approximated itself to the foreign material, 
the cell throws out pseudopodia in such a fashion as to encircle the 
foreign body ; as opposite pseudopodia meet the cell resumes in so far 
as possible its normal form and the material is enclosed in the cell 
protoplasm. These two stages in the process of phagocytosis have 
been reduplicated in experiments with non-living material. 

Digestion. The third stage of phagocytosis is the digestion of the 
foreign material. Such digestion is accomplished by secretions which 
are poured out by the cell protoplasm so as to constitute a small area 
of fluid about the ingested particle. By staining with dyes which show 
the acid reaction it has been found that although the cell protoplasm 
does not show acidity the fluid within the digestive vacuole is definitely 
acid in character. Attempts to extract this digestive fluid from protozoa 
have not been highly successful, but Mouton was able to extract from 
a symbiotic culture of amebae and colon bacilli an enzyme which is 
feebly proteolytic. This enzyme is capable of digesting colon bacilli 
which have been killed but does not act upon living colon bacilli. The 
intracellular digestion of these particles depends upon their solubility 
by the digestive fluids. The cell may take up insoluble particles, in 
which case the particles remain within the cells or are extruded with 
the excreta of the cells. 

Types of Phagocytic Cells. It is incorrect to think of leucocytes 
as identical with phagocytes, for numerous other body cells show this 
capacity, including the eosinophiles, the endothelial cells, the pulp cells 
of spleen and lymph-nodes, connective tissue cells, including bone cells, 
striated muscle cells and giant cells. It is probable that the lymphocytes 
and the mast cells exhibit no phagocytic activity. Metchnikoff divided 
phagocytes into microphages and macrophages. The microphages 
include particularly the neutrophilic leucocytes and the eosinophilic 
leucocytes, the important phagocytes of the circulating blood. The 
macrophages include the other cells mentioned above, the most important 
being the endothelial cells. It is perfectly true that the endothelial cell 
circulates in the blood, but apparently its most important activity is in 
the tissues and body spaces. The microphages are the more sensitive 
of the two groups and react not only to chemical stimuli but also to 
tactile and physical influences. 


Functions of Phagocytosis. Phagocytosis plays an important part 
in the entire life of the mammalia, even though the differentiation of 
many cells excludes them from this function. The destruction of 
erythrocytes in spleen, liver and bone marrow is in part due to phago- 
cytosis. Involution of the uterus after pregnancy, involution of senile 
ovaries, decrease in substance of the brain and other organs in old age 
are due to phagocytosis. Metchnikoff has laid considerable stress upon 
the activity of phagocytes in the atrophic processes of old age. Rind- 
fleisch claims to have demonstrated that phagocytes are active in the 
breaking down and removal of gouty deposits in and about joints. The 
fixed tissue phagocytes which play a part in the physiological destruc- 
tion of red blood-corpuscles have been designated by Kyes as 
hemophages. In various animal species the blood destruction accom- 
plished by the hemophages may be carried on predominately in one 
organ or another, the site of destruction, however, being constant for 
a given species under normal conditions. Pearce and his co-workers 
have shown that extensive blood destruction increases the phagocytic 
activity in the spleen and liver. They have also shown, as has been 
confirmed by us, that the removal of the spleen results in an assump- 
tion of hemophagocytic activity by the endothelial cells of the lymph- 
nodes. Gary has demonstrated that the injection of foreign red 
blood-corpuscles markedly increases the hemophagocytic activity of the 
recipient, not only in the spleen, which normally plays the important 
part in destruction of the red cells, but also in other organs. The 
resistance of the organism to foreign bodies, either living or inert, 
is partly the result of the same process. 

Under abnormal circumstances the removal of tissue and cell 
detritus is due in part to phagocytosis. In the inflammatory reaction 
following the introduction of foreign bodies, especially infective bac- 
teria, phagocytosis is the first line and most important defensive 
mechanism against invasion. Dusts inhaled into the lungs are taken 
up by mononuclear phagocytes or macrophages and conveyed to neigh- 
boring lymphatics and lymph-nodes, thus preventing accumulation on 
the respiratory membrane. In inflammation the circulation is slowed 
in the small vessels of the neighborhood, thus permitting the accumu- 
lation of leucocytes on the inner wall of the vessels. They then migrate 
through the vessel walls by ameboid movement and because of chemo- 
tactic attraction continue through the tissues to the irritating sub- 
stances. If the latter are bacterial the leucocytes attempt to ingest 
and destroy them. Thus it can be seen that phagocytosis is an im- 
portant process in the normal physiology of the body and perhaps 
even more so in the pathological physiology of defense against disease. 

The material to be ingested by phagocytes in part determines the 
type of cell which participates. The microphages are especially active 
in taking up bacteria, whereas the macrophages are active in ingesting 
inert tissue detritus. Nevertheless, macrophages often take up bacteria, 
as in tuberculosis, and, as has been shown by Kyes, by Bull and by 
Hopkins and Parker, pneumococci, typhoid bacilli and streptococci are 

FIG. 16. Microscopic drawing showing the phagocytosis 

of gonococci by the polymorphonuclear leucocytes in 

urethral pus. 


removed from the circulation by endothelial cells lining blood-vessels. 
Microphages may also play a large part in the removal of tissue detritus 
and may take up pigment as in malaria. 

Experimental Demonstration. The experimental demonstration of phago- 
cytosis in mammals is comparatively simple, as the following experiment from 
Metchnikoff will show. The blood of a bird, such as goose, hen or pigeon, is 
selected because of the fact that the nucleated erythrocytes are easily distinguished 
from those of mammals. Defibrinated bird blood mixed with equal parts salt 
solution is injected (about 3.0 c.c.) into the peritoneum of a healthy guinea-pig. 
Material is removed for study by means of finely drawn out glass pipettes, drops 
being placed on slides for study with or without subsequent staining. Within 
the first hour the leucocytes seem to have disappeared from the peritoneum. 

The disappearance is particularly striking when bacteria are injected and 
was interpreted by Metchnikoff as a destruction of the phagocytic cells, a 
phenomenon which he called phagolysis. At the end of from one to two hours 
exudate may be withdrawn which shows numerous cells, particularly macrophages. 
The macrophages show ingestion of the nucleated erythrocytes and at from 
twenty-four to forty-eight hours exhibit digestive vacuoles and partial digestion 
of the erythrocytes. 

At the end of three days the digestion is practically complete. 
Metchnikoff has shown that immunization will definitely limit the ap- 
pearance of phagolysis. Sanarelli, however, maintains that the disap- 
pearance of the leucocytes is not due to phagolysis but rather to the 
fact that the leucocytes of the peritoneal cavity and of the blood 
accumulate in the epiploic appendages into which the bacteria are 
likely to be carried by the lymphatic stream. Here, he asserts, bac- 
teriolysis and phagocytosis progress actively. Hence the disappearance 
of the cells from the exudate. 

A similar experiment may be performed with a suspension of pigment, as 
for example 5.0 c.c. finely-divided suspension of cinnabar (red mercuric oxide). 
This shows no digestion but active phagocytosis and a rapid transfer to re- 
gional lymph-nodes. 

Phagocytosis of bacteria may be very well demonstrated with colon bacilli. 
It is desirable in this instance to excite some exudation before the introduction 
of the colon bacilli. This may be produced by injecting about twelve hours 
previously 10.0 c.c. sterile bouillon or aleuronat suspension. This may be done 
in the evening and the following morning the guinea-pig is ready for the injection 
of a 24-hour bouillon culture or a 24-hour slant agar culture suspended in salt 
solution. The subsequent phenomena are similar to those following the injection 
of bird blood. 

The Mechanism of Phagocytosis. In earlier experiments of this 
sort several questions as to the mechanism of the process arose. That 
the bacteria do not actively penetrate into the phagocytes has been 
demonstrated by direct observation of the ameboid action of the cells 
and is concluded also by analogy from the fact that non-motile bacteria, 
non-motile cells, such as erythrocytes, and inert bodies, such as cinna- 
bar, are readily ingested by the phagocytic cells. That the bacteria are 
not killed before ingestion is shown by the fact that cultures may be 
successful in the case of anthrax bacilli shortly after they have been 
taken up by phagocytes. This may also be illustrated by the following 
experiment with the use of neutral red as a vital stain. This stains only 
dead cells and imparts no color to living cells. A warm hanging drop 
preparation of the exudate from a guinea-pig injected with colon 


bacilli as outlined above may be mixed with a drop of I per cent, 
neutral red in isotonic salt solution. At first the extracellular bacteria 
show no stain, and but few of the intracellular bacilli take the stain. 
As time goes on the number of intracellular organisms taking the stain 
increases until they are completely digested. Metchnikoff interpreted 
the coloration of the bacteria as being due to an acid digesting fluid 
formed by the cell, but we are unable to state at the present time 
whether the digestion of the bacteria is due to a special ferment or 
due to the same ferments that digest the cells themselves after they 
are destroyed. 

The Physical Basis of Phagocytosis. The mechanism of phagocy- 
tosis both as regards immunity and biology in general has been the 
the subject of much investigation. There are those who have main- 
tained that the ameba or the leucocyte, in spite of the absence of a 
nervous -system, exhibits individual intelligence in the selection of the 
material it takes up, but the bulk of experimental evidence would place 
the phenomenon largely on a physical chemical basis. There are im- 
portant differences between free living amebse and the phagocytes of 
higher animal life, such as the ectosarc and endosarc of the amebse, 
its pulsating vacuoles, variety of pseudopodia, conjugation and cyst 
formation, but there are resemblances in movement, form, nutrition and 
ultimate genesis which form a basis for many comparisons. That the 
life activities of the ameba can be closely simulated by non-living 
materials has been known for many years, but the most important 
stimulus to these studies in recent years has been given by the work 
of Jennings. A fundamental conception necessary to understanding 
the physical basis of ameboid motion and phagocytosis is that of the 
phenomena of surface tension. Wells expresses the matter most 
clearly and concisely as follows : " Imagine a drop of fluid suspended 
in water let it be a drop of protoplasm, or oil, or mercury ; the drop 
owes its tendency to assume a spherical shape to the surface tension, 
which is pulling the free surface toward the center and acting with the 
same force on all sides. The result is that the drop is surrounded by 
what amounts to an elastic, well-stretched membrane, similar to the 
condition of a thin rubber bag distended with fluid. If at any point 
in the surface the tension is lessened, while elsewhere it remains the 
same, of necessity the wall will bulge at this point, the contents will flow 
into the new space so offered and the rest of the wall will contract ; 
hence the drop moves toward the point of lowered surface tension. 
Conversely, if the tension is increased in one place the wall at this 
point will contract with greater force than elsewhere, driving the con- 
tents toward the less resistant part of the surface, and the drop will 
move away from the point of increased tension." The experimental 
demonstration of this phenomenon is relatively simple. A drop of mer- 
cury is placed in a nitric-acid solution and near it is placed a crystal of 
potassium dichromate. A yellow color diffuses out from the dichro- 
mate; as the color reaches the mercury the latter begins to move 
toward the crystal. This is the result of oxidation of the adjacent 


surface of the mercury drop whereby the surface tension of this side 
is lowered, thus causing the progressive movement in the direction of 
the dichromate crystal. Similarly a drop of clove oil in a mixture of 
glycerol and alcohol will move about and send out pseudopodia in much 
the same manner as an ameba. The movement depends upon the solu- 
bility of the clove oil in alcohol, but the glycerin retards the diffusion 
and thus determines a certain degree of irregularity in the movements. 
If strong alcohol be introduced near the clove oil the surface tension 
of the oil is reduced and it moves toward the alcohol. Heat applied 
near one side of the drop will also lower the surface tension, and it 
moves toward the point of heat positive thermotaxis. These experi- 
ments illustrate the physical basis of ameboid movement, but do not 
explain ingestion of particles. For this purpose a drop of chloroform 
may be placed in water and brought near a variety of objects, such as 
glass particles and small pieces of shellac, paraffin and glass. Such a 
drop will flow around a piece of shellac and dissolve it. A piece of 
glass covered with shellac will be taken up, the shellac dissolved and 
the piece of glass then extruded. If a long " hair " of shellac is 
brought into contact with the chloroform, the former will be bent in 
the middle, pseudopodia will extend along it and it will finally be 
curled up inside the drop and dissolved. These various activities of 
the oil drop or chloroform drop resemble in detail the activities of 
amebae under similar circumstances and may be understood as indi- 
cating that the process of phagocytosis is based on definite physical 
laws. The experiments do not explain all the phenomena, however, 
and must be interpreted as solving the problem only partially. Various 
food particles are not soluble in the cytoplasm of the ameba, bacteria 
are not soluble in the cytoplasm of the leucocytes, but in each instance 
must be digested in some way. Furthermore, the phagocytes have the 
property of taking up inert and insoluble particles such as coal dust 
and other pigments, substances which cannot exert chemotaxis nor 
alter surface tension. The artificial ameba does not assimilate, it 
merely dissolves. An additional differentiation between the leucocytes 
and the ameba is the fact that the ameba is a free living organism 
capable of nourishing itself independently of life within another or- 
ganism. On the other hand, the leucocyte depends upon the blood for 
its nutrition and differs in ameboid movement and irritability from 
the free living ameba. Thus we must conclude that the problem of 
phagocytosis is not solved by these experiments and that the life activ- 
ities of these cells are not as yet explainable on a purely physical basis. 
Influence of Temperature on Phagocytosis. Madsen and his 
school have made accurate studies of the influence of temperature 
on phagocytosis. They have shown that within certain limits the 
phenomenon of phagocytosis increases with the degree of tem- 
perature. Starting at a point of =*= 5 C., the phagocytic power 
increases with temperature up to the normal temperature of the species 
from which the phagocytic cells are derived. In cold-blooded animals, 
on the other hand, the temperature of the environment within certain 


limits appears to have no influence whatever on the phagocytic activity 
of their cells. Calderone and Runfola have recently studied the in- 
fluence of temperature upon phagocytosis in the frog and find that 
phagocytosis proceeds actively between 5 and 40 C., but ceases when 
a temperature of 42 C. is reached. 


Introduction. Early in the study of phagocytosis it was noted 
that immune animals respond to the introduction of the antigenic 
bacteria by a greater degree of phagocytic activity than normal animals. 
This was interpreted by Metchnikoff as being due to " stimulins " 
which were supposed to augment the activity of the phagocytic cells. 
The first study of importance in contraindication of MetchnikofFs con- 
ception of stimulins was that of Denys and Leclef in 1895. They 
showed in a study of streptococcus immunity in rabbits that the leuco- 
cytes of normal and immune animals took up the bacteria equally 
well, but that both varieties of leucocytes acted much more powerfully 
when immune serum was added. They indicated that the process of 
immunization did not augment the phagocytic power of the leucocytes 
and concluded that in their opinion the antitoxic substance acts not 
upon the leucocyte but upcfn a poison enclosed within the bodies of the 
microbes or dissolved in the medium, the poison acting to protect the 
bacteria against the attacks of the leucocyte until neutralized by the 
immune substance in the serum. The observations were confirmed by 
other investigators and later Denys and Leclef showed that whereas 
extremely virulent bacteria are taken up by leucocytes in normal serum 
to only a slight degree, the addition of an immune serum markedly 
increases the phagocytosis. Little progress was made until after the 
discovery by Leishman whereby the study of phagocytosis could be 
carried out in vitro. Modifying this method, Wright and Douglas in 
1903 published the first of a series of experiments which have built up 
in large measure our modern conception of the influence of serum on 
phagocytosis and the practical use of bacterial vaccination in the treat- 
ment of disease. They showed conclusively that it is the activity upon 
the bacteria of some substance in the blood which favors phago- 
cytosis and they named the substance opsonin. By treating the bacteria 
with serum, then washing them to remove the serum from the sur- 
rounding medium and finally mixing with a leucocyte emulsion in salt 
solution they showed that phagocytosis proceeds actively. Similar 
treatment of the leucocytes by serum produces no augmentation of their 
phagocytic activity. Thus it was shown that the serum does not stimu- 
late the leucocytes but rather prepares the bacteria so that they may 
more readily be ingested, hence the term opsonin (Gr. opsono to pre- 
pare food). There is some variation, however, in the way the serum 
operates in the case of different bacteria. Tunnicliff and Davis have 
shown that fusiform bacilli and influenza bacilli can be taken up readily 
independently of the presence of serum. There are, of course, different- 
degrees of facility with which bacteria can be taken up, varying from 


those which absolutely require the intervention of an opsonin 
and those mentioned above, which apparently need little or no par- 
ticular opsonization. 

Experimental Demonstration. For the experimental demonstration of 
opsonization it is necessary to have washed leucocytes, bacterial suspension and 
blood serum. Large quantities of leucocytes may be obtained by injecting 5.0 
c.c. aleuronat suspension into a guinea-pig's peritoneum and withdrawing the 
exudate at the end of twelve to twenty-four hours. These may be suspended 
in five to ten volumes normal saline, gently mixed and centrifuged, the process 
being carried out three times, when the cells are said to have been washed three 
times. If human leucocytes are desired, 10.0 c.c. saline sodium citrate are placed 
in a centrifuge tube and 2.0 c.c. blood added. The tube is centrifuged at high 
speed, whereupon a layer or " cream " of leucocytes collects at the upper level 
of the cell mass. The cream can be removed by a drawn-out nipple pipette 
and the cells washed as indicated for the peritoneal exudate. The bacterial 
emulsion can be made from a twenty-four-hour slant agar culture of staphylo- 
coccus pyogenes aureus by adding 10.0 c.c. salt solution, allowing to stand for 
ten to fifteen minutes and then rotating the tube between the palms of the hands. 
This is pipetted into another tube and for safety may be killed by heating in a 
water bath at 55-6o C. for two hours. The serum may be obtained by allowing 
blood to clot and then drawing off the serum. Small quantities may be obtained 
by the use of a tube such as shown in Fig. 8. Having these ready, 0.5 c.c. 
bacterial emulsion are mixed with o.i c.c. serum and incubated for one-half 
hour, then washed three times and the organisms resuspended in 0.5 c.c. saline. 
Several capillary pipettes are made from glass tubing (5 mm. bore) and the 
upper end flanged so as to take a rubber nipple. A mark is made with a grease 
pencil about 2 cm. from the tip, which serves as a volume indicator. (Fig. n.) In 
the experiment one volume bacterial suspension, one volume bacterial emulsion and 
one volume serum or saline are drawn into the pipette each in succession to 
the mark, permitting a small amount of air to enter before the next volume is 
taken up so as to permit of exact measurement of the volume. These are blown 
into a watch crystal and mixed by blowing in and out several times ; then taken 
into the capillary again and the end sealed. After incubation at 37 C. for 
fifteen minutes the tip is broken, the mixture dropped on slides or cover slips, 
spread, dried and stained with Wright's stain or some other modification of 
the Romanowsky stain. Then the number of bacteria in a given number of 
leucocytes (20 to 50 or more) are counted and the average calculated. A sample 
protocol follows : 



per cell 

1. Leucocytes (washed) -f bacteria (untreated) -f serum 22 

2. Leucocytes (washed) -j- bacteria (untreated) -j- NaCl I 

3. Leucocytes (washed) -j- bacteria (treated) -f- NaCl 14 

In the above protocol it is seen that the leucocytes exhibit a slight capacity 
for taking up bacteria independently of the presence of serum, but that this is 
much augmented either in the presence of serum or by previously treating the 
bacteria with serum. 

Normal Opsonins. As has been indicated, the phagocytosis of bac- 
teria and other cells is greater in immune than in normal animals, the 
difference being due to increase in the opsonin content of the serum 
of the immune animal. It was soon observed that the opsonin of the 
serum of normal animals could be destroyed by heat to 60 to 65 C. 
for 10 to 15 minutes; whereas the opsonin of immune animals is not 
destroyed by heat of 62 to 63 C. for forty-five minutes. Similarly 
exposure to light at room temperature leads to deterioration of normal 
opsonin in a few days but has practically no effect on immune opsonin. 
These differences in behavior were at first thought to constitute an 


actual difference in the nature of normal and immune opsonin, but 
this view has now been almost entirely abandoned. In the discussion 
of this change of view it is essential to present first the development of 
work in regard to the normal opsonin. Conservative workers were 
not disposed to accept the opsonin as a new form of antibody and 
from the ease of deterioration of the normal opsonin thought that it 
was identical with complement. Furthermore, it was shown that fixa- 
tion of complement by a hemolytic system or sensitized bacteria re- 
moves the opsonin, that yeast cells, cell detritus and bacteria will absorb 
both opsonin and complement, that blood serum and edema fluids 
contain parallel amounts of opsonin and complement, that certain body 
fluids, such as the aqueous humor of the eye, contain neither complement 
nor opsonin. Nevertheless, the removal of complement, as by heating, 
does not, as Hektoen has shown, remove all the normal opsonic power 
of the serum; and the fixation of complement by a hemolytic system 
or by sensitized bacteria still leaves slight opsonic power in the serum. 
The addition of fresh serum to a slightly active heated serum restores 
the activity practically to normal in much the same manner as a 
hemolytic amboceptor may be reactivated by complement. The fol- 
lowing example taken from Cowie and Chapman and slightly modified 
serves to illustrate this reactivation. The substances indicated in the 
protocol are added to leucocyte and bacterial emulsions and the figures 
given are for the bacterial count per leucocyte: 

1. Unheated (normal) serum 15-44 

2. Salt solution 0.18 

3. Heated serum 57 C 1.08 

4. Normal unheated serum, diluted i to 15 1.56 

5. Heated serum + normal serum diluted I to 15 1240 

6. Two volumes unheated normal serum 16.08 

Thus it will be seen that heating the serum reduces the phagocytic 
index from 15.44 to 1.08; that normal serum, diluted so that its 
phagocytic index is reduced to 1.56, added to heated serum, raises 
the index to 12.40, much higher than can be accounted for by the 
total indices of the two components. It can then be concluded that 
the normal opsonic power of serum depends upon two factors, a weakly 
acting thermostable element and a thermolabile element which markedly 
adds to the combined power of the mixture. Cowie and Chapman 
have shown that at o C. the thermostable element of opsonin is ab- 
sorbed by the bacteria, but that the thermolabile element remains in 
the supernatant fluid and is capable of reactivating a heated serum. 
It has also been demonstrated by absorption experiments that the ther- 
mostable element is specific. Numerous continental workers contradict 
this statement, but their studies have, for the most part, ignored the 
existence of the thermostable element of normal opsonins. Hektoen 
has shown that saturation of the bacteria with opsonin and heating so 
as to destroy the thermolabile part leaves the bacteria in such condi- 
tion that they cannot absorb any more opsonin from another serum. 


Moore has found that in guinea-pigs " the complement titer varies 
with the opsonic index and in the same direction." These facts, to- 
gether with the fact that vaccination with bacteria will increase specifi- 
cally the opsonic content of the blood suggest a close similarity of 
opsonins to agglutinins and amboceptors. The resemblance to agglu- 
tinins is only relative for as we have seen the thermostable element of 
opsonin is markedly augmented in activity by the addition of fresh 
serum, whereas agglutinins are not affected in any way by the addition 
of complementary substance. Hektoen has shown that in the process 
of immunization the curves of opsonin and agglutinin production are 
nearly parallel, but that heating does not influence the agglutinin and 
markedly depresses the opsonic action, the latter being restored by the 
addition of fresh normal serum. Levaditi, in a study of the site of 
formation of opsonins, showed that certain organs rich in agglutinin 
contain no opsonins. The thermostability and specific absorption of 
opsonins suggest similarity to amboceptors, but the amboceptors are 
not capable of acting without complement whilst the opsonin is capable 
of acting independently of fresh serum. The fresh serum augments 
the activity of the thermostable element of opsonins but is not an 
absolute essential for activity. That the opsonin is not identical 
with hemolytic and bactericidal amboceptors is indicated by the fact 
that there are such amboceptors in sera which have no opsonic power; 
that in sera which show both amboceptors and opsonins there is no 
parallelism between the activity of the two. Sera may be strongly 
opsonic for certain bacteria and yet contain no bactericidal amboceptor. 
Much of the material quoted above has been worked out in connection 
with immune opsonins, but nevertheless it is safe to conclude that the 
opsonic action of normal serum depends upon the operation of two 
elements, a thermostable element which behaves as a " facultative >:> 
amboceptor and a thermolabile element which, if not identical with, 
resembles complement most closely. 

Immune Opsonins. As has been indicated, it is possible by im- 
munization to increase to a very considerable degree the opsonic activity 
of serum. The immune opsonins were considered as of a constitution 
different from the normal opsonin because of the claim that the appli- 
cation of heat did not alter their activity. Dean showed, however, that 
this assumption is not true for he found that heating to 60 C. definitely 
though not very markedly reduces the opsonic activity of immune serum, 
and that reactivation takes place on the addition of a fresh normal 
serum. The following protocol shows the phagocytic index as deter- 
mined by the use of various sera and mixtures : 

Normal serum 11.9 

Heated immune serum 7.1 

Heated immune serum + normal serum 33.0 

Hektoen reached the same conclusion with the hemopsonic power of 
rabbits immunized to goat erythrocytes, diluting the serum so that it 


showed minimal opsonic power and no hemolytic action. One protocol 
from his work serves to illustrate. 

Heated immune serum Fresh guinea-pig serum Phagocytosis 

O.OOI 4 


Levaditi and Koessler showed that a serum which contained anti- 
complement by virtue of immunization with complement, when added to 
an immune opsonin, noticeably reduces the opsonic power. 

The full activity of the immune opsonin depends, as can be seen, 
from the above experiments, upon a thermostable and a thermolabile 
element, as is true of the normal opsonin, but the activation by fresh 
serum in case of the thermostable element of immune opsonin is pro- 
portionately much less than activation of thermostable normal opsonin 
by fresh serum. Reference to the activation of a hemolytic amboceptor 
by complement shows that a given amount of complement will activate 
a very small amount of amboceptor in greater proportion than a large 
amount of amboceptor. The thermostable fraction of opsonin has 
been referred to as a facultative amboceptor, because the action of the 
thermolabile part is not essential. Assuming this interpretation to be 
correct and assuming that the thermolabile element operates as a com- 
plement, it is a simple matter to infer that this complement would have 
a proportionately larger action on the facultative amboceptor of normal 
opsonin, which is present in very small amount, than on the similar am- 
boceptor of immune opsonin, which is present in relatively large amount. 

Bacteriotropins. Neuf eld and his school maintain that the immune 
opsonin is a body which operates only in the presence of complement 
and that the tropins, bacteriotropins and cytotropins are bodies appear- 
ing in serum which has been rendered complement-free, and which 
exhibit a capacity for so altering bacteria or cells that they are easily 
taken up by phagocytes. Levaditi and numerous other authors agree 
that Neufeld has shown that the tropins are not identical with those 
amboceptors which lead to cytolysis, but also agree that Neufeld has 
not succeeded in demonstrating that the tropins are antibodies distinct 
and apart from the thermostable element of immune opsonin. 

Opsonins for Cells other than Bacteria. Numerous substances, 
including vegetable cells, such as yeasts, and bacteria, as well as a 
variety of animal cells, may undergo phagocytosis when influenced by 
opsonins. In connection with phagocytosis of animal cells the work of 
Hektoen and his collaborators has been most extensive. The investiga- 
tions have thrown much light on the general study of opsonins and, di- 
rected particularly toward erythrocytes, have shown that the same 
general laws governing the phagocytosis of bacteria operate in the 
phagocytosis of erythrocytes. Neufeld and Handel have shown that 
emulsions of fat droplets in protein-containing media can serve as 
excitants of the formation of specific opsonic sera but conclude that in 
these instances the protein capsule of the fat droplets which serves to 
stabilize the emulsion is the important factor in the phenomenon. Led- 


ingham has also shown that the injection of melanin produces a specific 
opsonic serum and others have shown that carbon granules, cinnabar, 
carmine, etc., are phagocyted much more readily in the presence of 
serum than otherwise. In these latter instances it seems probable that 
the serum provides a protein capsule for the pigment granules, thus 
facilitating the action of opsonin, but at the present time no satisfactory 
explanation has been offered for the production of a specific immune 
opsonin following the injection of melanin. Neufeld and Ungermann 
point out the difficulty of satisfactory measurement of phagocytic action 
against pigment granules, and it is possible that this source of error 
may be sufficient to throw doubt on the results claimed to have been 
obtained with insoluble pigments. 

Specificity and other Characters of Opsonins. The specificity of 
the immune opsonins is clear-cut, as has been shown by numerous in- 
vestigators. An immune opsonin produced by vaccination with staphyl- 
ococci shows a marked influence on the phagocytosis of the antigenic 
organisms but none whatever on non-related organisms such as colon 
bacilli. As in the case of other immune bodies, group reactions are 
demonstrable. Vaccination with typhoid bacilli leads to the formation 
of immune opsonins which operate in high degree on the antigenic 
organism and also to less degree on closely-related organisms such as 
those of the paratyphoid groups. Dean, in working with serum dilu- 
tions in order to demonstrate that an optimum concentration of opsonin 
may not necessarily be found in undiluted serum, reports the following 
experiment. This may be interpreted as showing an inhibition zone in 
the stronger concentrations, although the differences are so slight as 
to fall within the limit of experimental error. 

Dilution of serum Phagocytic index* 

o 9-7 

1-2 9.6 

1-4 10.0 

1-8 8.2 

1-16 8.5 

1-32 64 

* Average number of bacteria ingested per leucocyte. 

Influence of Phagocyte and Ingested Elements. The foregoing 
paragraphs have considered the influence of serum on phagocytosis, but 
detailed studies have shown that certain considerations in regard to both 
the bacteria and the leucocytes exercise some influence. Neufeld pointed 
out that bacterial cultures from ten to twenty-four hours old are best 
for in vitro experiments. The reaction takes place best when the bac- 
teria are suspended in equal-parts broth and physiological salt solution, 
but in ordinary laboratory practice salt solution is used without the 
addition of broth and whatever deterring action is exercised by the salt 
is constant in the series of experiments. The thickness of the sus- 
pension is of importance since very thin suspensions determine a 
reduction in phagocytic index as compared with thicker suspensions. 
The optimal density of the suspensions varies with different bacteria 


and must be determined, in exact work, for the organisms under investi- 
gation. The more homogeneous the emulsion, the better the phago- 
cytosis observed. Numerous investigators have shown that under 
experimental conditions, bacteria killed by chemicals or by heat are 
phagocyted at precisely the same rate as living organisms. Further- 
more, the previous staining of the organisms has no deterrent action 
on phagocytosis. 

Relation of Bacterial Virulence. The relation of bacterial viru- 
lence to phagocytosis has been the subject of much research since 
Marchand first showed that virulent streptococci are taken up hardly 
at all under conditions where avirulent streptococci are phagocyted 
with avidity. He demonstrated that this difference is not due to the 
vitality of the bacteria, for when killed by heat at 60 C, 1.8 per cent. 
HC1, 2.5 per cent. Na 2 CO 3 or 90 per cent, alcohol, the virulent forms 
show the same resistance to phagocytosis. Wright and also Levaditi 
showed that the same difference is observable in the case of phago- 
cytosis, without the intervention of opsonins. Rosenow confirmed 
Marchand's results by the use of freshly-isolated virulent pneumococci. 
Reduction of virulence of thirty-six strains by repeated cultivation on 
media resulted in increased susceptibility to phagocytosis; and a res- 
toration of virulence by animal passages led again to decreased phago- 
cytosis. There is, however, no absolute parallelism between virulence 
and susceptibility to phagocytosis. Markl, von Gruber and Futaki, as 
well as Lohlein and others, found that anthrax bacilli and plague bacilli 
when taken from culture material are actively phagocyted in vitro even 
though highly virulent for animals. If removed from a guinea-pig's 
peritoneum after having grown there for several hours, they are no 
longer phagocyted in vitro. In animal experiments they are at first the 
victims of active phagocytosis in vivo, but after several hours are re- 
sistant to phagocytosis. Proper staining shows that in the resistant 
stage the organisms show definite capsule formation. These experi- 
ments indicate that the resistance is entirely a function of the bacteria, 
but that there is some interdependence between the bacteria and the 
opsonin is indicated by the experiments of Ungermann, who worked 
with pneumococci virulent for mice in doses as small as 0.000,001 c.c., 
but not injurious for rabbits in doses as large as i.o c.c. He found 
that mouse serum has no opsonic action and that rabbit serum acts 
energetically. After repeated cultivation so as to reduce virulence for 
mice the organisms are opsonized by mouse serum. Von Bockstaele 
and also Denys and von den Bergh were able to see leucocytes in the 
presence of a normal serum approach and even break up chains of viru- 
lent streptococci without engulfing them; if a strong immune serum 
were added, there resulted active phagocytosis. In summary, these 
various experiments show that the possession of virulence by an organ- 
ism confers upon it the power of resisting opsonization, that this power 
has some relation to the susceptibility of the particular animal whose 
serum is used for opsonization, that the resistance to opsonization is 
not lost on the death of the bacteria, and that in certain instances this 


resistance is accompanied by capsule formation. Levaditi believes that 
the resistance of virulent bacteria is dependent upon some alteration 
of the bacterial membrane (which alteration determines in all prob- 
ability the virulence of the organism) and also perhaps on the formation 
by the bacteria of an anti-opsonic or anti-phagocytic substance. In the 
latter connection Tschistowitsch and Jurewitsch claim to have shown 
that on washing, virulent pneumococci lose their resistance to phago- 
cytosis, but that submitting the organisms to the action of the material 
in the washings restores them again to their resistant state. They con- 
sidered that the salt solution removed in the washing a secretion which 
they called antiphagin. This work has not been confirmed and can- 
not be regarded as establishing beyond question the existence of 
an antiphagin. 

Influences Operating upon Phagocytic Cells. In the preliminary 
paragraphs of this discussion the stimulin theory of Metchnikoff was 
dismissed with a simple statement that such a theory exists. Never- 
theless, the leucocytes and their possible alterations are of considerable 
importance in phagocytosis, and while it is true that increased phago- 
cytosis resulting from immunity is not the result of stimulins, neverthe- 
less, it is possible to augment the activity of these cells. Neisser and 
Guerrini gave the name lencostimulants to certain substances which 
directly act upon the leucocytes. According to Manwaring and Ruh, 
numerous antiseptics in proper concentration exhibit a stimulating 
action. According to others, calcium chloride, magnesium salts, 
potassium iodide, iodoform, fat soluble substances (except cholesterol), 
substances facilitating oxidation, pepton, quinine in certain low con- 
centrations, nucleinic acid, similarly excite increased phagocytosis. 
Marbe has extracted a thermostable body from the thyroid gland which 
excites phagocytosis. The demonstration that the action of these various 
substances is upon the leucocytes depends upon the use of decreasing 
dilutions of the substances in the presence of sensitized bacteria and 
washed leucocytes. 

Metchnikoff showed the influence of heat on the leucocytes in 
experiments which are tabulated as follows : 

Degree of heat Time of heating Phagocytic index 

40 C. 15 minutes 18 

45 C. 15 minutes 8 

50 C. 15 minutes 3 

55 C. 5 minutes 1.2 

60 C. 5 minutes o 

60 C. 30 minutes o 

In addition to heat, alterations of OH ions, alterations of osmotic 
pressure, cholesterol, reduction in amount of electrolytes, potassium 
ions, alcohols, ether, quinine and certain other of the leucostimulants 
in high concentrations act upon the leucocytes to depress their phago- 
cytic activity. 

Analysis of Mechanism of Phagocytosis. The mechanism of 
phagocytosis includes the approach of phagocytes and the object to be 


phagocyted, the ingestion of these objects and in the case of living 
objects their death ; finally the digestion of bacteria and other suitable 
objects. The approach of the cells and the phagocytable objects is, 
according to Mesnil and his co-workers and also Levaditi, due to a 
physical chemical reaction and not dependent on the life of the leu- 
cocyte. If leucocytes are injured by heat to 45, 50 or 60 C., by refrig- 
erator temperature, by shaking, by grinding, and then mixed with bacteria 
and inactivated immune serum, the bacteria become clumped about 
the leucocytes. This reaction may be observed even if the tubes are 
laid in melting ice. The leucocytes that have been killed or paralyzed 
will not ingest the bacteria. The " anchoring " of leucocytes and 
bacteria will not occur unless specific opsonin is present in the serum. 
It occurs with fragments of leucocytes as well as other cells of the 
leucocyte series, such as myelocytes and myeloblasts. Thus the affinity 
may be expressed as existing between the protoplasm of the phagocytic 
cell and the sensitized bacteria or other phagocytable object. 

Although actual ingestion of objects may be shown in the case of 
artificial amebae it does not occur in the leucocyte unless the cell is 
alive and in possession of its capacity to project pseudopodia. Hence 
this stage of phagocytosis must be bound up with the life processes of 
the phagocyte. 

From the earlier studies of Metchnikoff it has been known that the 
bacteria, after phagocytosis, are killed and digested. The influence 
of the blood fluids in this phenomenon has been the subject of much 
study and conflicting results. Metchnikoff and his co-workers were of 
the opinion that the leucocytes contain complement, which, as has been 
shown in previous chapters, is required for the action of bactericidal 
and bacteriolytic amboceptors. They believed that this complement is 
liberated only upon the destruction of the leucocytes as seen in phag- 
olysis for they were unable to find complement in plasma. They inter- 
preted the presence of complement in serum as due to the death of the 
leucocytes during clotting of the blood. This interpretation has been 
combated by numerous observers who have been able to demonstrate 
complement in plasma. In support of the conception that the death of 
the bacteria is due to completion of the bactericidal amboceptor-antigen 
complex by complement in the leucocyte, is Bordet's work with cholera 
vibrios. Using immune sera which contained bacteriolytic amboceptor, 
he found no lysis except in those bacteria that were within phagocytic 
cells. As opposed to this conception, the work of Neufeld and his 
collaborators has shown that sera may be richly opsonic without con- 
taining lytic amboceptors, and in these instances the bacteria are 
destroyed and digested by the phagocytes. The destruction varies with 
different organisms and with the virulence of the organisms, the more 
virulent being less readily killed than the avirulent strains. Bacteria 
may be cultivated on artificial media after having been ingested, a 
certain amount of time being necessary to kill the organisms. The 
act of digestion is closely bound up with that of killing the organisms. 
The presence of a proteolytic ferment in leucocytes has been known 


since the work of Mueller and Jochmann, who placed the leucocytes 
of animals upon plates similar to those used for bacterial cultivation. 
At incubator temperature, the leucocytes exhibit distinct proteolytic 
power. Recent studies by Van Calcar would appear to indicate that 
the organs of the body which secrete digestive ferments have some 
influence over the ferments existing within the leucocytes. He found, 
for example, that after the removal of the stomach the leucocytes of 
the animal were unable to act as peptic digestors. Similarly the 
removal of the pancreas destroys the ability of the leucocytes to act 
as tryptic digestors. In summary it is necessary, in order to accom- 
plish destruction and digestion, to sensitize the organisms and to have 
present active living leucocytes. Opsonization will not in itself kill or 
digest the organisms ; therefore, the phagocyte must furnish some 
substance which either completes the action of the opsonin or of itself 
can kill and digest the organisms. The fact that phagocytosis in all 
its stages may occur in slight degree independently of opsonin would 
indicate that the phagocyte is the important element in death and diges- 
tion of the phagocyted object. Recent work by Bachmann would indicate 
that the leucocytes of normal and immune animals have a different 
capacity for protecting against disease. Sixty times more leucocytes 
from a normal animal were needed to save a guinea-pig against typhoid 
infection than the number required from an immune animal. In the 
case of anthrax the leucocytes from immune animals were eighty times 
more active than those from normal animals. That these studies can 
be interpreted as indicating a variation in the actual phagocytic power 
of leucocytes is open to considerable question. 

It is probable that the affinity of the phagocyte and phagocytable 
object is, in large part if not entirely, a physical chemical phenomenon 
entered into on the one hand by the cytoplasm of the leucocyte and 
other cells and, on the other hand, the opsonized organisms or other 
object. The ingestion, death and digestion are dependent upon the life 
function of the phagocyte, which is capable of liberating a microbicidal 
and microbilytic substance capable of combining with the microorgan- 
ism to bring about its death and destruction. 

Introduction. rStudies of inflammation and of other cellular activ- 
ities have made it clear that body cells play an important part in resist- 
ance to disease that is not entirely explained by the phagocytic capacity 
of certain of the cells. As has been indicated, cells other than the 
polymorphonuclear leucocyte and the large mononuclear cell possess 
the property of phagocytosis, but this is occasional and presumably 
not of great importance. It seems desirable, however, to discuss the 
mechanisms of resistance as influenced by properties of the leucocytes 
other than phagocytosis, by activities of the lymphocytes and by the 
cells and fluids which play a part in inflammation. 

Bactericidal Extracts of Leucocytes. The destruction of bacteria 
within the phagocyte so impressed Metchnikoff that he assumed that 


extracellular destruction is accomplished by identical destructive 
agents. The demonstration that extracellular destruction of bacteria 
(bacteriolysis) requires the participation of amboceptor and comple- 
ment had little influence on Metchnikoff's views, inasmuch as he was 
convinced that complement originates solely in the leucocytes. As we 
have stated (page 129) the more recent examination of this problem 
makes it certain that complement exists free in the blood. Further 
study, more particularly of opsonins and bacteriotropins, has made 
it apparent that the mechanism of intracellular digestion is quite differ- 
ent from that of extracellular lysis. Nevertheless, the leucocytes may 
contribute to the extracellular destruction of bacteria. Buchner showed 
that the exudation, produced in the pleura of rabbits and dogs by injec- 
tions of aleuronat, removed and killed by freezing and thawing, pos- 
sesses the property of killing bacillus coli. Denys and Kaisin produced 
pleural exudates by injection of killed staphylococci and removed the 
cells by centrifugation. The clear supernatant fluid was actively bac- 
tericidal. Others have made extracts of exudates, and of leucocytes 
obtained from the blood, and have demonstrated that a bactericidal 
substance is to be obtained. Certainly these substances are yielded up 
after the destruction of the cells and, according to Petterson, they 
may be secreted by the cell during its life. The substances are resistant 
to a temperature of 56 C., but after inactivation by heat to 75 to 80 
C. they cannot be reactivated by the addition of fresh extracts. This 
substance or group of substances has been called endolysin by Petterson 
and leucine by Schneider. It is not identical in all animals since that 
from dogs, rabbits and guinea-pigs kills bacillus proteus and bacillus 
anthracis, but that from the guinea-pig and cat fail to kill the bacillus 
typhosus and the spirillum cholerae. 

Bachmann has recently reported on a so-called leucocyte antibody, 
" antkorps leucocytaire," which is distinct from the bactericidal endo- 
lysin. It appears in the leucocytes of immunized animals and may serve 
to produce passive immunity in other animals. It is found only in the 
polymorphonuclear leucocytes and may be extracted in normal serum. 
It is effective in protecting guinea-pigs against intraperitoneal injection 
of the specific organism and also acts beneficially and specifically upon 
established infections. A temperature of 75 C. destroys this substance, 
but if the material is well diluted and gelatin added, the same degree 
of heat serves to destroy the non-specific bactericidal substances (endo- 
lysins) but permits the specific leucocyte antibody to remain active. 
Bachmann believes that the persistence of this antibody in the leuco- 
cytes explains the fact that individuals retain immunity to certain 
diseases after the serum antibodies are no longer demonstrable. 

Leucocyte Enzymes. In contrast to the bactericidal substances 
extracted from leucocytes it is possible to obtain enzymes. Leber, in 
a study of inflammation, found that sterile pus can liquefy gelatin and 
the study of this proteolytic enzyme, the leucoprotease, has been ex- 
tended by Miiller and Jochmann, Opie, Longcope and others. This 
leucoprotease may be purified by precipitation with alcohol more par- 


ticularly from glycerol extracts and the desiccated precipitate may be 
preserved almost indefinitely. In the moist state temperatures of from 
50 to 65 C. increase its activity, but at 70 to 75 C. it is destroyed. 
It acts best in weakly alkaline or neutral medium, and is inhibited by 
acid. It differs from trypsin in that it is much less active; it does not 
require activation by any such substance as enterokinase, and exists 
within the cells in an active state rather than in the form of zymogen. 
It differs from the bactericidal extracts in that it cannot kill bacteria, 
but may digest them after their death. The blood possesses an anti- 
enzyme, but when the cells accumulate in bulk, as in the case of inflam- 
matory exudates, the anti-enzyme is overbalanced and the protease 
dissolves necrotic cells, dead bacteria and other detritus. It is of 
considerable importance in the resolution of lobar pneumonia. In 
addition the leucocytes are stated to contain amylase, diastase, catalase, 
oxidase, peroxidase, nuclease and an ereptic ferment, but there appears 
to be a difference of opinion in regard to lipase. 

Opie has described an additional ferment in areas rich in large 
mononuclear cells, which acts best in a very weak acid medium. It is 
inhibited by temperatures of 50 to 65 C., by alkali and by the con- 
centration of HC1 (0.2 per cent.) favorable for the action of pepsin. 
He was able to demonstrate this ferment in hyperplastic lymph-nodes 
rich in large mononuclear phagocytes. It is closely related to the 
enzymes of tissue autolysis. The acid medium which favors the action 
of this enzyme inhibits the activity of anti-enzyme. 

Leucocyte Extracts for Therapeutic Purposes. Petterson noted 
that when leucocytes are placed in contact with blood serum for several 
hours the mixture is more actively bactericidal than the serum alone 
or salt solution extracts of the leucocytes. This led to experiments in 
which he injected leucocytes simultaneously with anthrax bacilli into 
dogs and found a moderate protection by this treatment. Opie similarly 
observed that the injection of leucocytes and tubercle bacilli into the 
pleura of dogs led to less severe manifestations than when tubercle 
bacilli alone are injected. Probably the most important contributions 
to the treatment of disease by leucocyte extracts are the studies of Hiss 
with the collaboration of Zinsser, Dwyer and others. Hiss obtained the 
leucocytes from pleural exudates produced by the injection of aleuronat 
suspensions. This was centrifuged before clotting occurred and the 
cells emulsified in distilled water. Either the leucocytes or the leu- 
cocytes and supernatant fluid were employed for treatment. From 
experiments with staphylococcus, pneumococcus, streptococcus, meningo- 
coccus and typhoid bacillus infections in rabbits, it was determined that 
protection was afforded by the extracts and that the infection was 
favorably influenced if therapeutic doses were given as late as twenty- 
four hours after infection. Encouraging results were also obtained in 
the treatment of human cases of pneumonia, meningitis, staphylococcus 
infections, erysipelas and other diseases. In analyzing the beneficial 
effects of this form of treatment, it was found that the bactericidal 
properties of the extracts are not sufficiently great to explain their 


influence, they do not materially favor phagocytosis but appear to 
augment the migration of leucocytes to a slight degree and possibly are 
of importance in this way because of the fact that they exert positive 
chemotaxis. Zinsser states " we are inclined to believe at present that 
the beneficial effects of leucocyte extracts are based on the same prin- 
ciples as those which determine the reactions following on the injection 
of bacterial and any other protein." To us it appears that this method 
is to be included in the category of non-specific therapy previously 
discussed (page 30). 

Specific Hyperleucocytosis. Following upon the earlier sug- 
gestion of Bordet, Gay and his collaborators found that immune animals 
exhibit a much higher degree of leucocytosis following the injection 
of the organism to which they had been immunized than do normal 
animals. For example, rabbits immunized to typhoid bacilli reacted 
to subsequent injections of typhoid bacilli. with blood counts of as high as 
150,000 leucocytes per cmm., whereas normal rabbits showed a reaction 
of only 40,000 to 50,000 leucocytes per cmm. This phenomenon of spe- 
cific hyperleucocytosis has been contradicted by McWilliams, who found 
no important difference in response between normal and immune animals 
and further states that typhoid immune rabbits react in essentially the 
same degree to colon bacilli as to typhoid bacilli. Others have confirmed 
the work of McWilliams. Zinsser and Tsen found a slight favorable 
difference in animals immunized to Gram negative cocci and a somewhat 
more marked difference in those immunized to Gram positive cocci, not 
in any case, however, to the degree indicated by Gay. There seems 
little reason for believing that a specific hyperleucocytosis plays any 
important part in resistance to infection. This, however, is not to be 
construed as an argument against vaccination, since the latter procedure 
is important in the production of specific opsonins, agglutinins and other 
immune bodies. Any response to vaccination in the form of leucocytosis 
must be regarded as only in small part if at all specific and is probably 
of the same nature as the leucocytic response to the injection of non- 
specific proteins and their products. 

The Lymphocytes. Lymphocytes appear in inflammatory areas as 
the result of infection, but accumulate in largest amounts in chronic 
inflammatory areas where, in most instances, the active infective agent 
is no longer present. The part they play in the phenomenon of inflam- 
mation and in protection against infection is not understood. From 
the work of Opie it seems probable that the lymphocytes may be, in 
part, the source of the ferment which he describes as operating in 
weakly acid media. As pointed out above, this ferment was obtained 
from hyperplastic lymph-nodes. The lymphocytes are said to contain 
a lipase, and it is suggested that the large collections of these cells 
about tuberculous foci may serve by the action of the lipase to break 
down the waxy shell of the bacilli. The lymphocyte is stated to possess 
phagocytic properties, but these are at best very slight and probably 
play no important part in resistance to disease. It has long been noted 
that the presence of tumors in the body often excites a neighboring 


chronic inflammatory reaction in which lymphocytes appear in con- 
siderable numbers. J. B. Murphy and his collaborators have put to 
the test of experiment the hypothesis that lymphocytes are of import- 
ance in resistance to cancer. By the use of the X-ray they were able 
to destroy practically all the lymphoid tissue of the body of animals and 
found in these animals a decreased resistance to transplanted cancer. 
Immunity already established to cancer was also destroyed by this 
procedure. Similarly there was a lowered resistance to tuberculosis 
and to anterior poliomyelitis. In tuberculosis the lymphocyte constitutes 
a large element in the inflammatory reaction, and this is true also in the 
later stages of acute anterior poliomyelitis. Although small doses of 
X-ray may stimulate lymphocyte production, Murphy and his asso- 
ciates found that dry heat produces a more durable increase in the 
circulating lymphocytes. By increasing the lymphocytes in this fashion 
they demonstrated " the establishment of a high degree of immunity 
to certain transplantable cancers in mice," regardless of whether these 
cancers naturally showed a high or low percentage of successful inocula- 
tion. The same was found to be true in regard to the implantation of 
grafts from spontaneous cancers into the animals from which the 
grafts were removed. This subject has also been studied by F. C. 
Wood and associates in the Crocker Laboratory. They found that mice 
with lymphatic leucemia show no demonstrable immunity to tumors. 
They found that reduction of the total leucocyte count by means of 
X-ray or radium produces no increase in the successful transplanta- 
tion of normal tissues. They found further that successful transplan- 
tation of the guinea-pig fibrosarcoma is not influenced by the use of 
X-ray. They selected an immune strain of rats, exposed them to X-ray 
and found no change in susceptibility to transplantable tumors. They 
found that the use of X-ray on rats in which a highly virulent tumor had 
been implanted did not prolong the life of the tumor. Wood states 
that " it is, therefore, evident that the lymphocyte is in no way corre- 
lated with cancer immunity." Sittenfield also found that artificial 
lymphocytosis has no effect whatever on tumor growth. It is of further 
interest that in human cancer the lymphocytes collect about the slowly- 
growing rather than the rapidly-growing tumors and that the metastases 
are frequent in the lymph-nodes. The later experiments of Murphy 
on the lymphocytosis induced by heat have not received as yet extensive 
examination ; therefore, the question remains open. Murphy's experi- 
ments are so well conducted that it is difficult to be assured that the 
lymphocytes play no part. The work of Wood carried out on a large 
number of animals is of especial significance and would indicate that 
the lymphocyte plays no such important part in resistance to cancer as 
Murphy's work appears to indicate. 

Platelets. In 1901 Levaditi noticed that following the injection of 
cholera vibrios they were often found clumped around small masses 
of platelets. The phenomenon was called thigmotropism. Govaerts 
subsequently demonstrated that the clumping is influenced by the action 
of opsonins. LeFevre found that anti-bacterial immunization increases 


thigmotropism because of the increase in activity of opsonins. Further 
study may throw light on the mechanism of the process, but at present 
its function is obscure. 

The Influence of Inflammation. Infection always produces some 
degree of inflammatory reaction, but this varies considerably with the 
type of infectious organism and with the capacity of the host to react. 
The exudate comprises the polymorphonuclear leucocyte, the lympho- 
cyte, the plasma cell, the large mononuclear cell, certain other less 
important cells, the red blood-corpuscles, serum and fibrin. The part 
played by the more important of these cells is indicated above. As far 
as we can determine, the red blood-corpuscles appear more as an 
accident of the process than as an essential part of it. The fluid part of 
the exudate rapidly coagulates with the formation of fibrin and serum. 
There can be no doubt that the serum serves in certain measure to 
concentrate in the inflammatory areas those immune bodies qualified 
to offer resistance to the invader and its products. In case toxic 
products are present, these are diluted by the serum and the subsequent 
absorption of the serum with this diluted poison aids in its elimination 
from the body. The fibrin network probably serves in a certain measure 
to wall off and limit the growth of the invading organism. It also 
serves as a scaffolding for the support of newly-growing fixed tissue. 
Very early in the course of an acute inflammation the connective tissue 
cells proliferate. They may be phagocytic, but this property is of 
little significance. Certainly the most important function of the con- 
nective tissue in resistance to infection is the formation of a tissue 
which serves to limit the advance of the infection. The newly-growing 
connective tissue, with its capillaries, constitutes granulation tissue and 
the resistance of granulation tissue to infection is a matter of common 
observance. As the inflammation becomes chronic the connective itssue 
becomes denser and thereby provides a much less permeable wall than 
is found in the earlier stages of the process. The production of a local 
inflammation leads to the formation of an exudate which by virtue of 
the polymorphonuclear leucocytes opposes to infection the important 
process of phagocytosis; the liberation of bactericidal substances and 
of enzymes from the leucocytes serves to aid in resistance and to liquefy 
dead tissues and dead bacteria. Under favorable circumstances addi- 
tional enzymes are provided by the large monuclear cells and lympho- 
cyte. The large mononuclears aid in the removal of dead material by 
virtue of their phagocytic powers. The fluid part of the exudate brings 
into the process the immune bodies of the circulating blood, serves to 
dilute toxic products and favors their absorption and elimination in 
dilute form. The fibrin, granulation tissue and cicatrization act as de- 
limiting elements and operate toward the localization of the process. 









Introduction. A summary of the hypotheses concerning the con- 
stitution of complements shows that there are three important views 
offered, namely the " pluralistic " conception of Ehrlich and Morgen- 
roth, the " dualistic " of Metchnikoff and " unitaristic " of Bordet. 
As has been explained, the view of Metchnikoff that complement might 
be a " macrocytase " or a " microcytase " depending upon its cellular 
origin has been abandoned by most immunologists. Thus the conflict 
has been, and in certain measure still is, between the views of Ehrlich 
and of Bordet. Bordet and Gengou in demonstrating that the same 
complement is called on for bacteriolysis as for hemolysis, discovered 
the phenomenon named by them complement fixation (" la fixation 
d'alexine ") which we employ in sharp contradistinction to complement 
deviation. The latter term implies the anchoring of complement by 
free amboceptor units, whereas fixation signifies the entrance of the 
complement into combination with antigen and amboceptor. In brief, 
they showed that if complement is utilized in the process of bacteriolysis 
it is not available for hemolysis. 

The Bordet-Gengou Phenomenon. -The primary experiment was 
performed with plague bacilli, the serum of a horse immunized to 
plague bacilli, fresh guinea-pig serum (complement) and sensitized red 
blood-corpuscles, i.e., corpuscles saturated with a specific hemolytic 
immune serum. They mixed an emulsion of plague bacilli, the anti- 
plague horse serum and complement. This mixture was left at room 
temperature for five hours and then the previously-sensitized erythro- 
cytes added, the mixture incubated and observed. No hemolysis 
appeared, although the corpuscles were often agglutinated by the hemo- 
lytic (and hemagglutinative) immune serum. Naturally, such an ex- 



periment required numerous controls, the complete series being indi- 
cated in the following protocol : 

1. Plague bacilli -j- immune horse serum + complement 4* sensitized cells = 

No hemolysis. 

2. Plague bacilli + normal horse serum -j- complement + sensitized cells = 


3. immune horse serum -j- complement + sensitized cells = 

4. normal horse serum -f- complement + sensitized cells = 

5. Plague bacilli -j- immune horse serum + sensitized cells = 

No hemolysis. 

6. Plague bacilli -f- normal horse serum + sensitized cells = 

No hemolysis. 

Throughout the experiment all the sera were inactivated except the 
fresh guinea-pig complement and all mixtures stood at room tempera- 
ture for five hours before the addition of the sensitized erythrocytes. 
Hemolysis in tube 2 shows that normal horse serum does not serve 
as an amboceptor or sensitizer for the plague bacilli and therefore 
does not prevent the complement from entering into combination with 
the sensitized erythrocytes. Tubes 3 and 4 contain no bacterial 
antigen, cannot utilize complement and therefore hemolysis appears. 
Tubes 5 and 6 show that the bacteria are not hemolytic and that 
neither of the inactivated immune sera nor the inactivated normal horse 
serum contain complement for the completion of the amboceptor-cell 
complex. Bordet and Gengou showed that the same phenomenon could 
be observed with a wide variety of bacteria and specific immune sera 
both of human and lower animal origin; these operate to fix both 
guinea-pig and human complements, so as to prevent combination of 
these complements with hemolytic immune sera from several species. 
Furthermore, the immune sera so fixed might be specific for several 
varieties of erythrocytes. Muir and Martin found, however, that 
whereas most complements can be fixed in such experiments, this is not 
universally true and occasional complements are met with which do 
not enter into certain combinations. Furthermore, the process could 
be reversed so that the fixation of complement in hemolysis prevented 
its action to bring about bacteriolysis of sensitized bacteria. Thus it 
appeared that one and the same complement operates for the produc- 
tion of both bacteriolysis and hemolysis. This demonstration of the 
unity of complement has been combated by later work, and it now 
appears that there are certain exceptions to the rule, although it can 
generally be accepted. 

Laboratory Demonstration of the Bordet- Gengou Phenomenon. In 
order to demonstrate the phenomenon it is not necessary to use plague bacilli, as 
others serve the purpose equally well. The readily obtainable typhoid bacillus 
and typhoid immune serum can be used with good results. In setting up the test 
it is important to bear in mind the fact that numerous substances may interfere 
with the activity of complement, and among these are certain concentrations of 



bacterial emulsions and extracts. Therefore, it is necessary to be sure that the 
amount of bacterial emulsion used in the test is not "anti-complementary," but 
yet in sufficient concentration to operate well. The emulsion is made from a 
twenty-four-hour slant agar culture (see page 81 for preparation) and may be 
killed by heat or formalin. The preliminary titration may be set up as follows : 



i-io dilution 






0.5 c.c. 

0.5 c.c. 


0.5 c.c. (2 doses) 

0.5 c.c. 


0.4 c.c. 

0.5 c.c. 

0.5 c.c. (2 doses) 

0.5 c.c. 



0.3 c.c. 

0.5 c.c. 


0.5 c.c. (2 doses) 

0.5 c.c. 



O.2 C.C. 

0.5 c.c. 

0.5 c.c. (2 doses) 

0.5 c.c. 



O.I C.C. 

0.5 c.c. 


0.5 c.c. (2 doses) 

0.5 c.c. 



0.5 c.c. 

i i 

0.5 c.c. (2 doses) 

0.5 c.c. 



Each tube should be made up to a volume of 2.0 c.c. with salt solution before 
primary incubation. If convenient the erythrocytes may be sensitized by the 
previous addition of amboceptor. In the protocol C.H. indicates complete 
hemolysis, P.H. partial hemolysis and no hemolysis. 

The Test. The results given indicate that 0.5 c.c. bacterial emulsion is defi- 
nitely anti-complementary, but the 0.3 c.c. has no such influence. The last tube 
excludes hemolytic activity on the part of the emulsion. In order to be abso- 
lutely sure that the final test will not be misleading through the anti-comple- 
mentary action of the bacterial emulsion it is advisable to use the next smaller 
amount than the titration shows to be free of anti-complementary activity, which 
in this case is 0.2 c.c. This being the case 2.0 c.c. bacterial emulsion may be 
diluted with 3.0 c.c. salt solution, whereupon 0.5 c.c. of the dilution will contain 
0.2 c.c. original emulsion. The complement-fixation test may then be set up 
as follows : 











0.5 c.c. 
0.5 c.c. 
0.5 c.c. 


0.5 c.c. 


0.5 c.c. 

0.5 c.c. 
0.5 c.c. 
o.s c.c. 

0.5 c.c. 





I.O C.C. 
I.O C.C. 
I.O C.C. 







0.5 c.c 

0.5 c.c. 

0.5 c.c. 
0.5 c.c. 

0.5 c.c. 
0.5 c.c. 


I.O C.C. 
I.O C.C. 





0.5 c.c. 

I.O C.C. 

I.O C.C. 


1.5 c.c. 

I .O C.C. 

The first incubation permits of fixation of the complement by the bacteria 
and their specific immune serum and the second determines whether or not 
complement is free to act upon the sensitized erythrocytes. For sensitization of 
erythrocytes the hemolytic immune serum should be diluted so that 0.5 c.c. 
contains two units hemolytic amboceptor, then added to an equal volume 5 per 
cent, erythrocyte suspension. In the above test the immune serum is diluted, so 
that 2.5 c.c. contain ten units amboceptor; it is then added to 2.5 c.c. 5 per cent, 
erythrocyte suspension and the mixture allowed to remain at room temperature 
for one hour. The protocol given above shows, reading from below upward, 
that the hemolytic immune serum used for sensitization is not of itself hemolytic, 
that the complement is in sufficient concentration for hemolysis, that neither the 
bacterial emulsion nor the typhoid immune serum is anti-complementary in the 
amounts used. In the first tube the bacterial emulsion, specific anti-bacterial 
serum and complement interact so that the complement is not free to combine with 
the sensitized erythrocytes, whereas tube 2 shows that normal rabbit serum will 
not fix complement. 

Specific Character of the Test In order to elaborate the test and to show 
its specificity it is well also to titrate an emulsion of some other organism, for 
example, colon bacilli for anti-complementary activity at the same time the 
typhoid emulsion is titrated and in the same manner. If this shows anti-comple- 



mentary activity in a dose of 0.3 c.c., then o.i c.c. is used in the test. The fully 
controlled test would then be set up as follows : 




immune serum 
(i/io dilution) 

(l/io dilu- 

Salt solu- 








O^ c c 

0.5 c.c. 

o.s c.c. 


.0 c.c. 


o ? c c 

o ^ c c 

O 2^ C C 


o.s c.c. 

0.5 c.c. 

0.5 c.c. 

.0 c.c. 



o 5 c.c. 

0.5 c.c. 

o.s c.c. 

.0 c.c. 



o.s c.c. 

0.5 c.c. 

0.5 c.c. 


.0 c.c. 



0.5 c.c. 

0.5 c.c. 

0.5 c.c. 


.0 c.c. 



0.5 c.c. 

I.O C.C. 

i i 

.0 c.c. 




1.5 c.c. 

.0 c.c. 

Reading from above downward, the second tube shows 0.25 c.c. typhoid 
emulsion diluted 2 to 5, thus corresponding in bulk of original emulsion, to the 
bulk of coli emulsion in 0.5 c.c. of a 1-5 dilution. It is necessary to use the 
smaller bulk of coli emulsion in order to prevent anti-complementary activity. 
Both quantities of typhoid emulsion are sufficient to fix the complement, whereas 
the coli emulsion (tube 3) does not. The next three tubes which are controls show 
that neither typhoid emulsion, coli emulsion nor anti-typhoid immune serum 
have any anti-complementary activity. The last two tubes show that the com- 
plement is in sufficient concentration to operate and that the sensitized erythro- 
cytes will not of themselves hemolyze under the conditions of the experiment. 
If the results prove to be confusing it is necessary to make additional controls 
to determine if any of the reagents is hemolytic. This contingency is extremely 
rare if proper care is given in their preparation. The test in this form shows 
that the reaction is specific. 

Inhibition Zones. The phenomenon of complement fixation ex- 
hibits certain of the characters noted in regard to other immune reac- 
tions, not only in the titration of the reacting bodies but also in the 
formation of the so-called inhibition zones and in the group reaction. 
These latter features are best illustrated with the fixation of comple- 
ment by immune sera prepared from the use of dissolved protein. 
Gengou, a year after the publication of Bordet and Gengou, showed 
that the inoculation into an animal of dissolved proteins, such as egg- 
white, could lead to the formation of bodies which participate in com- 
plement fixation with the specific antigen. This was confirmed by 
Moreschi and later by Neisser and Sachs. The latter authors applied 
the reaction to the forensic determination of protein. Gengou was of 
the opinion that the immunization of animals with dissolved protein 
led to the formation not only of precipitins but also of complement-fixing 
bodies. The relation between these two immune substances will be 
discussed after presenting data concerning inhibition zones and group 
reaction. An experiment from the work of Neisser and Sachs serves 
to illustrate the fact that immune serum may be used in the reaction 
in such strong concentration as to inhibit fixation of the complement. 
For this purpose they arranged two series of tubes. In series A they 
placed decreasing amounts of the specific immune serum, a constant 
quantity of 0.2 c.c. of 1-2000 solution of the antigenic human serum 
and o.i c.c. fresh guinea-pig complement. In series B the same con- 
stituents were placed with the exception of the immune serum which 
was replaced in each tube by 0.2 c.c. salt solution. These mixtures 
were incubated at 37 C. and then sensitized red blood-corpuscles were 


added, followed by another period of incubation. In this particular 
instance they employed ox blood-cells and immune serum prepared by 
injection of ox blood-cells into the rabbit. 


Immune serum Complement fixation 

i-io dilution Series A Series B 

1.0 C.C. + 

0.75 c.c. 

0.5 c.c. 

0.35 c.c. 

0.25 c.c. +++ 

0.15 c.c. ++ 

O.I C.C. + 

O.O C.C. 

The above protocol shows that in the strong concentration of im- 
mune serum the fixation of complement is not as marked as in some- 
what weaker concentration. Nevertheless, there also comes a point 
when the concentration is too dilute to permit of fixation. The tubes 
in series B show that the concentration of human serum in itself is not 
sufficiently great to prevent the hemolytic reaction. Two points are 
of interest in this connection. In the first place, it is possible to add 
immune serum or other serum in amounts so large that the serum itself 
will have inhibitory action upon the complement. Under optimal con- 
ditions immune serum may be diluted to an extreme degree and still 
act as a complement-fixing body; for example, Friedberger, by the 
use of a well-prepared serum was able to demonstrate complement 
fixation by an immune serum diluted 1-1,000,000,000. The same deli- 
cacy has not been confirmed by other investigators and must be regarded 
as a scientific curiosity. The dilution of the antigenic protein can be 
carried to a considerable degree but not usually to the same degree as 
is possible with antiserum. 

Group Reactions. In the application of the complement-fixation 
test to the forensic determination of dissolved protein, Neisser and 
Sachs showed that the group phenomenon also appears. They also 
showed that the antigenic serum could be very much reduced in amount 
and still give complement fixation. The following protocol illustrates 
the manner in which such a demonstration may be made. In setting 
up the test there was used throughout a constant quantity of o.i c.c. 
immune serum prepared by the injection of human serum. The anti- 
genic serum was added according to the amounts indicated in the 
protocol. Complement was used in amounts of 0.05 c.c. The mixtures 
were incubated and then beef blood-corpuscles which had been sensitized 
with a specific anti-beef corpuscle serum were added, the mixtures 
again incubated and the degree of fixation determined. 


Amounts of Fixation with serum of 

antigenic serum Man Monkey Goat 

0.01 +++ +++ 

0.001 +++ 

o.oooi 4-M- + 

0.00001 . -f 



The above protocol shows that anti-human serum is capable of 
fixing complement in the presence of an amount of antigenic serum, 
which is considerably less in the case of human antigenic serum than 
in the case of monkey antigenic serum. Thus the group reaction is 
indicated by the fact that the serum of a closely-related species is in 
certain doses sufficient to produce fixation. Muir and Martin, also, 
were able to demonstrate similar reactions in several different 
animal groups. 

Relation of Complement-fixing Bodies to Other Immune 
Bodies. The fact that the treatment of animals with a protein in 
solution can lead to the development in the animal's serum of a capacity 
both for precipitating the antigen and combining with the antigen to fix 
complement suggests naturally that there may be some relationship 
between the two phenomena. Gay and Moreschi independently were 
able to show that precipitates formed by the action of a specific immune 
serum can so bind complement as to prevent its action upon a hemolytic 
system. The assumption is justified, therefore, that the two phenomena 
are very closely related and may indicate that complement fixation 
depends in part at least upon fixation of the complement by a precipitate. 
The question naturally arises then whether or not there may be com- 
plement fixation without precipitation or precipitation without com- 
plement fixation. Furthermore, a fundamental problem is whether or 
not the two activities of the antiserum depend upon two different 
immune bodies in the serum or upon the double capacity of the same 
immune body. Neisser and Sachs were able to show that complement 
fixation occurred with very much smaller amounts of antigen than does 
visible precipitation. As has been mentioned before, in reference to the 
delicacy of the reaction, it was pointed out that fixation of complement 
may occur with dilutions of 1-1,000,000,000, whereas visible precipita- 
tion has never occurred in such marked dilution of antigenic or of 
immune serum. Thus it can be concluded that the presence of a visible 
precipitate is not necessary for the fixation of complement, a statement 
amply corroborated by Muir and Martin. Wassermann and Bruck 
found that by permitting bacterial extracts to stand for a considerable 
time, the extracts were no longer precipitable in the presence of specific 
precipitating immune sera, whereas fresh extracts show beautiful pre- 
cipitation. Nevertheless, both new and old bacterial extracts were 
found to fix complement in the presence of the specific immune serum. 
Liefmann further showed that the action of heat may so alter the 
antigenic protein as to lead to differences in complement fixation and 
precipitation. He immunized rabbits with egg-white and found that 
after heating the egg-white it could be so changed that it was no longer 
precipitable by the immune serum but could still operate with the 
immune serum in complement fixation. 

Felke and also Garbat have found that anti-typhoid vaccination in 
man leads to the production of agglutinins, but to no or very slight 
production of complement-fixing bodies. Felke found that in the course 
of typhoid fever and during convalescence complement fixation could 


be demonstrated in addition to agglutination. Most of the preceding 
experiments indicate that the phenomena of precipitation and comple- 
ment fixation are not necessarily associated, but, on the other hand, 
cannot be interpreted to indicate that the immune serum contains two 
different immune bodies. Friedberger and Liefmann, working inde- 
pendently, showed, however, that heating an immune serum to 67 C. 
can destroy the precipitin in the serum without altering the capacity 
of the serum for participating in complement fixation. This experiment 
has been interpreted as indicating that precipitating and complement- 
fixing bodies represent independent activities but not necessarily that 
they are different bodies. Muir and Martin found that upon immuniz- 
ing animals they were able to demonstrate that the serum of these 
animals contained complement-fixing powers earlier than precipitins 
could be demonstrated. Altmann found that complement-fixation 
bodies appeared earlier than agglutinins for paratyphosus B and colon 
bacilli but with the use of typhoid bacilli both bodies appeared about 
the same time. As a converse of this demonstration, Moreschi im- 
munized birds with rabbit serum and found in contravention to his 
earlier work that he was able to produce a precipitin of very high titer 
without being able to demonstrate the power of complement fixation on 
the part of the immune serum. This was corroborated by Sobernheim. 
Liefmann was able to show a certain amount of difference in the activity 
of immune serum. He brought the immune serum in contact with the 
antigen at o C. for sufficient time to produce a considerable amount 
of precipitate. He then centrifuged the precipitate and found that the 
supernatant fluid at 37 C. was capable of fixing complement. Lebailly, 
by the fractional addition of antigen to the precipitating immune 
serum, was able apparently to separate the precipitating and comple- 
ment-fixing bodies. Arlo precipitated the antigenic and immune sera 
by means of CO 2 , thereby obtaining the globulins in the precipitate. 
In both instances the complement-fixing body was found in the redis- 
solved globulin fraction and the precipitating body was found in the 
supernatant fluid. This has been controverted by Bruynoghe, who 
maintains that euglobulins are capable of producing non-specific fixa- 
tion. Reviewing all this experimental evidence, it seems perfectly 
clear that complement fixation can and does occur independently of 
visible precipitation, a statement supported by a great mass of more 
recent investigation of the subject. None of these experiments, how- 
ever, can be safely interpreted as indicating that there are two separate 
bodies in the immune serum. Neufeld and Handel, however, appear to 
be definitely of the opinion that there are two separate bodies concerned. 
They found that sensitized cholera spirilla are capable of fixing the 
hemolytic complement at o C. but that at 37 C. the organisms will 
fix both hemolytic and bacteriolytic complement. They explain this 
by assuming that the fixation at higher temperature is due to the bacteri- 
cidal amboceptor but that the fixation at o C. is due to a separate sub- 
stance which they named the Bordet antibody. Such experimental 
evidence cannot be accepted as final. Sachs states that a priori it can 


be supposed that the antigenic protein can simultaneously combine with 
precipitins and with amboceptor. He offers the hypothesis that one 
immune molecule may contain different binding complexes, one, for 
example, combining with precipitins to produce a precipitate and the 
other combining with the antigen and the complement to produce fixa- 
tion. If this view be accepted, the experiment of Friedberger and Lief- 
mann, in which the immune serum was heated, indicates that of the 
two binding complexes the precipitating one is the more labile. It can 
very readily be seen that the interpretation of Sachs depends almost 
entirely upon an acceptance of the Ehrlich hypothesis of the structure 
of immune bodies. 

Dean has examined the question and finds that the optimal rela- 
tionship between antigen and immune serum for the production of 
precipitation is by no means necessarily the optimal relationship for 
complement fixation. Therefore, the two phenomena, as has already 
been pointed out, are by no means parallel. He is of the opinion, 
however, that this lack of parallelism is not necessarily an indication 
that the two things are entirely distinct and separate. He is of the 
opinion " that they represent two phases of the .same reaction." The 
complement fixation represents the earliest and more delicate stage 
of a reaction which, in its more marked manifestation, is seen by the for- 
mation of a precipitate. Zinsser has studied the matter carefully and has 
come to the conclusion " that the precipitation is merely a secondary, 
colloidal phenomenon, which may, or may not, coincide with the phase 
of greatest alexin (complement) fixation, according to other fortuitous 
conditions which may favor or retard flocculation." He found that a 
mixture of sheep serum and its specific immune serum showed com- 
plement-fixing activity only in the precipitate. On the other hand, in 
a mixture of a filtrate of typhoid bacilli and a specific immune serum 
both the precipitate and the supernatant fluid were capable of fixing 
complement. " From this it seems to follow that immunization with 
the more complex cellular elements has given rise to the precipitating 
antibodies present also in the anti-sheep serum, and in addition to 
this to sensitizers which are not precipitable (remaining in the super- 
natant liquid) and not present in the anti-sheep serum." He, therefore, 
is of the opinion that since both the antigen and the immune body are 
colloidal in character they may be expected to follow the laws of 
colloids. This may be interpreted to indicate that the contact of the 
mutually precipitating colloids must be present in optimal concentration 
in order to show a visible precipitation, but, on the other hand, the 
interaction of the two bodies which, in the quantities employed, 
show no visible precipitate, may be demonstrated by the comple- 
ment-fixation test. He states " that the visible precipitation would 
seem, therefore, to be a secondary phenomenon, the essential one 
being- the union of an antigen with a sensitizer by which it is ren- 
dered amenable to the action of the alexin " (complement). 

Is the Complement-fixing Body an Amboceptor? There arises 
further the question as to whether or not the body, which, in combina- 


tion with antigen, serves to fix complement, is to be regarded as an 
amboceptor (sensitizer). As has been shown in the discussion of 
cytolysins, it is possible at o C. to bring about a selective combination 
of hemolytic amboceptor with its antigen. Liefmann attempted to 
bring about a union of complement-fixing body and its antigen in this 
way but was unsuccessful. It is known that if a considerable excess 
of antigen or antiserum is present, complement may also be absorbed 
at o C. and in such an experiment as Liefmann's it is impossible to 
say that such an excess did not exist. Therefore, the experiment is 
not conclusive. Neufeld and Handel also attempted selective absorp- 
tion at 37 C. They showed that cholera vibrios and their specific 
immune sera fix the hemolytic complement at o C., whereas the 
bacteriolytic complement remains active. At 37 C. both complements 
are fixed. They are of the opinion that at o C. the complement-fixing 
amboceptor is bound to the hemolytic complement and that at 37 C. 
both the complement-fixing and bacteriolytic amboceptors are active. 
This experiment has been held to support the hypothesis of the multi- 
plicity of complements. They also found that an immune serum pro- 
duced by the injection of a certain water vibrio acted as a complement- 
fixing body with cholera spirilla but did not serve as a bacteriolytic 
amboceptor. This may be interpreted as indicating that the two im- 
mune bodies are distinct but does not prove the amboceptor nature of 
that body which enters into the phenomenon of complement fixation. 
It may very well be that the experimental conditions were not optimal 
to the reactions and that while investigators sought to separate two 
forms of complement they were working with one and the same body 
which operates somewhat differently under the diverse conditions. 
Sachs interprets the amboceptor as a body which brings about the union 
between antigen and complement but states that certain amboceptors 
may be toxic (lytic) and others, for example, those serving to fix com- 
plement, may be considered as atoxic. He considers that the differences 
in effect may be the result of a number of factors, including mass action 
and differences in combining avidity of the various reacting bodies. 
It would appear to us that Zinsser's interpretation in regard to pre- 
cipitins might also be applied here and that the lysis of cells may be an 
incident in complement fixation, certain conditions favoring lysis, others 
merely fixation of complement. If this be accepted, the complement- 
fixing body must be regarded as an amboceptor or sensitizer in the 
same sense as are the cytolysins. 

Activation by Complement. The utilization of complement in 
hemolysis serves so to fix complement that it cannot activate a bac- 
teriolytic amboceptor. Therefore, hemolysis exhibits the fixation of 
complement in association with lysis of the cells. Handel found that 
hemolytic and complement-fixing properties of an immune serum were 
parallel, but Muir and Martin observed marked differences. The latter 
investigators produced two immune sera, one against ox serum and the 
other against ox cells, both of which exhibited hemolytic and comple- 
ment-fixing properties. The immune serum prepared against ox cells 


laked the antigenic cells in doses of 0.0015 c.c. and fixed complement in 
the presence of o.ooi c.c. ox serum. The immune serum prepared 
against ox serum hemolyzed ox cells in doses of 0.05 c.c. but fixed 
complement when combined with only 0.000,001 c.c. of ox serum. The 
immune serum against ox serum had only about one-thirtieth the 
hemolytic power of the immune serum prepared against ox cells but was 
looo times more powerful in fixing complement. They found that 
ox cells can absorb hemolysin from an immune serum without removing 
the precipitating or complement-fixing activity and conclude, in oppo- 
sition to the hypothesis offered at the end of the preceding paragraph, 
that the complement-fixing body and the hemolysin are distinct and 
separate immune bodies. 

Fixation of the Complement of Natural Hemolysins. In the case 
of natural hemolysins the complement in many instances is apparently 
in a state of close combination with the -thermostable lytic body. The 
entrance of such complements into the phenomenon of complement 
fixation has only rarely been demonstrated and then only in the case 
of those naturally hemolytic sera in which it is possible to absorb 
hemolytic amboceptor at o C. without at the same time removing 
the complement. 

Nature of Antigen and Amboceptor. The chemical character of 
the antigen and amboceptor have been studied more particularly in 
connection with investigations of the Wassermann test and will be 
considered in the discussion of that application of complement fixation. 
It may be said at this place, however, that the complement-fixing 
immune body will resist the ordinary inactivating temperature of 56 C. 
and is therefore to be regarded as thermostable but is destroyed by 
75 C. for one hour. The antigen is thermostable in the same sense 
but is reduced in activity at 75 C. but not destroyed until 100 C. 
is reached. 

Inhibition of Complement other than by Fixation. Of great im- 
portance are the factors that exercise an influence upon complementary 
activity. Those which operate on the living animal have been discussed 
in the chapter on Cytolysins (see page 127). There was also presented 
a brief discussion of physical conditions such as heat, exposure to light, 
desiccation, etc. All these factors must be considered in interpretations 
of complement fixation, and in addition it is considered desirable to 
present certain other conditions which may be gathered into three classes 
(a) chemicals, (&) various tissues and fluids, (c) antisera. 

Anti-complementary Chemical Agencies. The salt concentration 
of the media for complement fixation is extremely important and reaches 
its optimum at a point isotonic with the body fluids. The action of 
complement is decreased in hypotonic and absent in salt free media. 
Examination of this phenomenon leads to the conclusion that such 
action is upon complement rather than upon amboceptor, and Ferrata is 
of the opinion that the important change is the splitting of the comple- 
ment into mid-piece and end-piece. Under these circumstances the 
mid-piece may be bound to the amboceptor-antigen complex, but as 


the end-piece remains free, complementary activity does not appear. 
This explanation, however, is only hypothetical, is not entirely supported 
by other experiments and fails to take into account the influence of salts 
on colloidal suspensions and solutions. Excesses of salts also interfere 
with the action of complement, but on dilution to isotonicity the function 
is immediately restored. Therefore, the salts do no permanent injury 
to complement. Hektoen and Reudiger, as well as Manwaring, offer 
the explanation that ionization of the salt permits of a union with com- 
plement which is easily reversible. Certain salts, such as those of 
bile acids, as well as sodium oleate, permanently injure complement. 
The salts are of themselves hemolytic, but serum, inhibits their hemo- 
lytic activity. The amounts which are hemolytic in themselves com- 
pletely inhibit complement and by virtue of the presence of serum 
cannot produce lysis. 

Acids and alkalis in considerable concentration permanently destroy 
complement, but if the injury be due to a dilute alkali the comple- 
mentary activity may be restored by neutralization. It appears that 
moderate concentrations of acids destroy complement without restora- 
tion by neutralization. Dilute acids accelerate hemolysis and for this 
reason are to be avoided in accurate work with complement fixation. 
Certain protein products, such as urea (also urea sulphate) and guani- 
din are anti-complementary. 

Colloids may also inhibit complement as, for example, the organic 
colloids, glycogen, inulin, pepton, albumose, gelatin, etc., as well as 
inorganic colloids, such as quartz sand, kaolin and carbon. Numerous 
indifferent chemical precipitates, such as colloidal iron hydroxide and 
protein precipitates inhibit complementary activity. It is possible that 
in certain measure this may depend upon their interference with the 
complement amboceptor and antigen behaving as interacting colloids. 

The influence of lipoids on complementary activity is of great im- 
portance, particularly in the Wassermann test, but we may mention at 
this point that lecithin, cholesterol, protagon and tristearin in sufficient 
concentration are anti-complementary as well as certain lipins, including 
the neutral fats, olive oil, triolein, etc. Added, finally, to the list of 
chemical agents are boric acid, benzoic acid, formalin, sodium fluoride, 
sodium sulphite and extracts of certain spices. 

Anti-complementary Action of Cells, Tissue Extracts and Body 
Fluids. As was pointed out by von Dungern, most animal cells either 
in the form of emulsions or cells may inhibit the activity of comple- 
ment. Muir found that the stroma of red blood-corpuscles enters into 
fixed combination with complement and that if washed red corpuscles 
are heated to 55 C. for twenty-four hours they also will combine 
directly. The union does not take place at o C. but occurs readily at 
37 C. The combination is apparently not dissociable. Not only animal 
cells but also a wide variety of bacterial emulsions or their filtrates 
as well as yeast cells fix complement. On the basis of the Ehrlich 
hypothesis this may be due to the union of complement with the com- 
plementophile groups of those sessile receptors of cells which by im- 


munization are overproduced and become free in the blood. Other 
investigations, particularly those of Landsteiner and von Eisler, indicate 
that the cell lipoids play a part in the union with complement. The 
material extracted from the cells by petroleum ether was found to be 
definitely anti-hemolytic and furthermore this was especially true if 
the cells used in hemolysis were from the same species as the lipoidal 
extracts. Landsteiner and von Eisler demonstrated in addition that 
cells treated with fat-dissolving agents were less susceptible to 
hemolysis than normal cells. They suggested the possibility that the 
fixing substance may be a lipoid protein combination. Bang and 
Forssman extracted cells with ether and found that an acetone soluble 
material could be recovered that was definitely anti-complementary. 
Dantivitz and Landsteiner confirmed this but found in addition that the 
fraction remaining in the ether, the acetone insoluble fraction, could 
fix normal amboceptor but not immune amboceptors. Thus it will be 
seen that the finer details of the anti-hemolytic powers of lipoidal 
extracts are still unsettled. As to the anti-complementary action of bac- 
terial extracts Zinsser suggests that it may be non-specific and com- 
parable to the anti-complementary activity, mentioned in the previous 
paragraph, of such inert substances as kaolin and quartz sand. 

The body fluids of importance in this connection are the tissue 
juices, certain pathological exudates and more particularly the blood 
serum. Camus and Gley found that a normal hemolysin may be in- 
hibited by the addition of a similar serum which had been inactivated. 
Miiller showed that a heated serum may inhibit the activity of other 
sera, and concluded that this was due to an anti-complementary activity. 
Extreme instances of this action have been reported by Kenneway 
and Wright. Muir and Browning demonstrated that inactivated sera 
homologous with those used as complement were more strongly anti- 
complementary than heterologous sera. They concluded that the action 
was due to the presence in the heated sera of complementoid which, 
at least partly, excluded the complement from union with the ambo- 
ceptor. Bordet and Gay found that a sufficient dilution of inactivated 
sera removed the anti-complementary action and therefore consider 
concentration of the serum a most important factor. This would indi- 
cate that the inhibition is, in general, against the reaction, although 
Sachs offers the suggestion that the dilution provides for a dissociation 
of complement and anti-complement. More proof than is now at hand 
is necessary in order to admit the existence of an anti-complement in 
the sense in which Sachs uses the term Of great importance is the 
work of Noguchi, who found that whereas heating the serum to 56 C. 
permits of the demonstration of anti-lytic powers, a temperature of 
70 C. considerably augments this activity. Noguchi was able to extract 
from both serum and cells by means of ether a substance, highly ther- 
mostable (90 C.), which exhibited the same anti-lytic properties 
as the serum. The removal of the ether extract left the serum free 
from anti-lytic activity. He named the substance " protectin " and 
believed it to be the source of the inhibiting action of serum. Noguchi's 


opinion is that the inhibiting action of serum is largely anti-com- 
plementary in nature, although in part the action may be upon the 
amboceptor. The great thermoresistance of the body in the serum 
argues against the assumption of an anti-complement in the strict 
immunological sense. The action may well be anti-complementary, 
but from the work of Bordet and Gay, as well as of Noguchi, it would 
appear that the concentration of colloids associated with a disturbance 
of lipoidal balance or combination must occupy a most important place 
in hypotheses concerning this phenomenon. Of practical importance 
is the fact that prolonged preservation of serum increases its anti- 
lytic capacity. 

Anti-hemolytic Activity of Immune Sera. In discussing the prop- 
erties of complement (see page 137) we mentioned the experimental 
evidence concerning the production of anti-lysins and anti-comple- 
ments by the injection of immune and normal sera. The anti-lytic 
activity of such immune sera was thought at first to be due to an 
anti-complement, but later was thought to be the result of action upon 
the amboceptor or sensitizer. It must be recognized, however, that the 
injection of a serum, whether it contain complement or immune ambo- 
ceptor, leads to the production of a precipitin and that such precipitins 
can be demonstrated in the immune sera containing the so-called anti- 
complement. As has been pointed out in the preceding discussion on 
complement fixation the presence of precipitates serves to fix com- 
plement and this probably accounts for the anti-lytic and anti-comple- 
mentary powers of the immune sera. 

The fact that agglutination of the red cells inhibits their lysis was 
pointed out independently by Handel and by Karsner and Pearce. This 
renders inadvisable the use for complement-fixation tests of sera which 
are strongly hemagglutinative. 












Introduction. The demonstration of complement fixation employs 
five reagents, syphilitic antigen, red blood-cells, syphilitic serum, hemo- 
lytic serum and the complement. Having any four of these known it is 
possible to determine the immunological nature of an unknown fifth 
reagent. This unknown may be an antigenic substance or may be an 
amboceptor. In the forensic tests for species proteins the unknown is 
the questionable protein which is employed as an antigen; in other 
tests the unknown may be bacteria or bacterial proteins. In the Was- 
sermann and other clinical tests the unknown is an amboceptor or 
similar substance, produced in the blood and other body fluids of the 
diseased subject. 

After preliminary experiments on animals, Wassermann, Neisser, 
Bruck and Schucht published in 1906 the results of a series of com- 
plement-fixation tests in cases of human syphilis and demonstrated the 


clinical value of the reaction. The widespread use of the reaction has 
led to marked advances in the understanding of this disease, its sequelae 
and its treatment. This application of the Bordet-Gengou phenomenon 
has enabled science to progress far toward the elimination of one of 
the greatest plagues of mankind. Wassermann and his collaborators 
had first shown that the Bordet-Gengou phenomenon was applicable 
not only to bacterial suspensions but also to bacterial extracts and from 
this developed the proposition that the causative agent of syphilis 
might act as an antigen in extracts from syphilitic organs. The test 
was originally performed with a salt solution extract of the liver or 
spleen of a syphilitic fetus (rich in treponema pallidum), inactivated 
human serum, guinea-pig complement, an inactivated hemolytic im- 
mune serum and sheep erythrocytes. All the reagents were tested and 
titrated to avoid factors of error and proper controls were instituted in 
each experiment. Much has been accomplished by further study in the 
hands of numberless investigators, but we shall limit our discussion 
to those features which are of fundamental importance in the under- 
standing and application of the test. 

The Antigen. The preparation of the antigen is one of the most 
important features of this test. It would be supposed that an extract 
of a pure culture of the treponema pallidum should give the most 
specific results. This, however, has not proved to be the case. It is 
difficult to grow the organism in pure culture and the method of culti- 
vation interposes difficulties in the way of obtaining pure extracts. 
Results are variable and therefore not so specific as with the use of 
other antigens. Until recently the organism had not been cultured in 
vitro and Wassermann and many of his successors were unable to 
utilize the method. Wassermann selected the organs of syphilitic 
fetuses, because they were known to contain large numbers of tre- 
ponemata, and from these made extracts in physiologic salt solution. 
He cut syphilitic fetal liver in fine pieces and mixed 100 grams liver 
with 360 c.c. physiologic salt solution and 40 c.c. 5 per cent, phenol 
solution. This was shaken for twenty-four hours, centrifuged and the 
supernatant fluid employed as antigen. Practical experience shows that 
these antigens vary considerably in strength and rapidly lose fixing 
power. Deterioration may result from light, air, warmth and freezing, 
so that the extract must be kept tightly stoppered in the dark at low 
but not freezing temperature. Marie and Levaditi dried and pulverized 
the liver in order to preserve it and made up salt solution extracts when 
needed. Morgenroth and Stertz preserved the organ in the frozen 
state. The subsequent work of Weil and of Lansteiner and their col- 
leagues indicated that tumor extracts, extracts of animal tissues and 
of normal human tissues would operate as antigens. More recently 
Varney and Baeslack have employed extracts of experimentally inocu- 
lated testes of the rabbit in that stage of infection when the organs are 
richly infiltrated with the treponema. 

Landsteiner, Muller and Potzl found that alcoholic extracts of 
guinea-pig heart serve admirably as antigen. Independently Porges 


and Meier showed that alcoholic extracts of normal or syphilitic fetal 
organs operate equally as well as the watery extracts of syphilitic or- 
gans. These studies demonstrated that the antigen in the Wassermann 
test is not necessarily derived from the treponema pallidum, is alcohol 
soluble and therefore is largely of lipoidal nature. Landsteiner, Miiller 
and Potzl extracted I. gram heart with 50. c.c. absolute alcohol but 
this method has been somewhat modified. For practical purposes 50 c.c. 
absolute alcohol are placed in a wide-mouth amber bottle and as 
guinea-pigs are killed in the laboratory the heart is freed from blood 
and connective tissue, cut into a few pieces and placed in the alcohol. 
When ten hearts are so collected they are dried and ground in a mortar. 
Ten grams of the dried powder are returned to the alcohol and the 
volume made up to 100. c.c. This is shaken for twelve hours and placed 
either at 60 C. for about twelve hours or at 37 C. for about five days. 
It is then filtered and the filtrate preserved in a cool, dark place. Further, 
a second extraction with alcohol of the first dried extract yields an 
antigen of greater value because it contains less lytic and anti-lytic 
substance, although it may be slightly weaker in fixing power. Appar- 
ently, however, the alcoholic extracts of syphilitic organs produce more 
specific antigens. To prepare such an antigen 100 grams syphilitic 
liver are freed from surrounding tissue, washed free of blood and cut 
into fine pieces- This is extracted in 1000 c.c. absolute alcohol for a 
week at 37 C., the flask being shaken several times daily. It is 
then filtered and titrated. 

Forges and Meier found that lecithin could, within certain limits, 
be substituted for the antigenic extracts. This naturally led to extensive 
investigation of the nature of the substance or substances concerned. 
The fact that ether extracts of alcohol soluble antigen, according to 
Levaditi and Yamanouchi, did not contain antigen led to the thought 
that salts of bile acids might serve as antigens. Neither lecithin nor 
salts of bile acids give consistent results in the actual test and at the 
present time no pure substance serves well as antigen. The importance 
of lecithin was further emphasized by the refined technic of Noguchi 
in preparing the so-called acetone insoluble antigen. This method ap- 
pears to be especially adapted to the use of normal human organs, 
particularly heart. The tissue is cut into fine pieces, mixed with five 
times its weight of absolute alcohol and placed at 37 C. for from 
five to seven days. It is then filtered and the clear filtrate evaporated 
in a dish by means of an electric fan or in a vacuum desiccator. The 
residue is taken up in as small a volume of ether as will permit solution 
and allowed to stand overnight. The clear supernatant fluid is decanted 
and slightly evaporated. To it is added four volumes of acetone. The 
supernatant fluid is poured off and the precipitate allowed to evaporate 
to a resinous consistence. Three-tenths of a gram of this mass is 
added to a mixture of i.o c.c. ether and 9.0 c.c. pure absolute methyl 
alcohol and preserved in a dark, cool place. According to certain re- 
ports, it would appear that this antigen gives positive results in cases 
which are negative with other antigens and in which syphilis has not 


been demonstrated by clinical examination. It is useful, how- 
ever, as a control of other antigens with which doubtful results have 
been obtained. 

The source of the lecithin appears to play some role in its value as an 
antigen; that from heart is most active, while that from liver, brain 
and egg yolk follow in the order named. An extract such as that 
recommended by Noguchi contains in all probability a mixture of lipoids 
and unsaturated fatty acids; Noguchi and Bronfenbrenner found the 
fixing capacity of such extracts to vary in accordance with the content 
of unsaturated fatty acids. Browning and Cruikshank found that the 
addition of cholesterol to the antigen augments the delicacy of the re- 
action and this method has found widespread use in this country, 
particularly through the work of Walker and Swift. The latter investi- 
gators recommend the addition to alcoholic extracts of human or 
guinea-pig hearts of 0.4 per cent, of cholesterol. In the hands of sev- 
eral workers this has so increased the fixing power of the antigen as 
to give positive results in the presence of non-syphilitic serum, the 
so-called false positive reactions, and with the development of the 
method of fixation at refrigerator temperature, to be described subse- 
quently, it has been discarded in several laboratories. Nevertheless, the 
cholesterolized antigens are found, in the hands of numerous workers, 
to show much less variation in fixing capacity than the non-cholesterol- 
ized extracts and for this reason are recommended for routine 
laboratory work. 

It would appear that the antigenic substance in the Wassermann test 
is not an antigen in the biological sense, for it can be obtained from 
tissues not the seat of a syphilitic infection and as has been shown by 
Fitzgerald and Leathes, upon injection into animals it does not lead to 
the formation of immune substances. 

The methods of preparing syphilitic antigens have been multiplied 
in great number and cannot be included in the scope of this book. Sim- 
plification of preparation has been attempted with variable results. 
Of interest is the method suggested by Ecker and Sasano. They quote 
Neymann and Gager to the effect that primary extraction of the tissue 
with ether removes substances of anti-complementary power but only a 
small amount of the lecithin. Ecker and Sasano suggest three ten- 
minute extractions with ether in the proportion of 25. grams ground 
and dried heart muscle to 50. c.c. ether. The material is then extracted 
for one hour with 75. c.c. 95 per cent, ethyl alcohol at boiling tempera- 
ture (78 C.) in a flask connected with a reflux condenser. An antigen 
of this sort has retained its original fixing power in this laboratory 
after more than a year. 

Nature of Syphilitic Antigen. Extracts of the treponema pallidum 
may serve as antigens and are true antigens in the biological sense. 
Craig and Nichols, however, found that alcoholic extracts of organ- 
isms closely related to treponema pallidum, as the treponema per- 
tenue and the treponema microdentium, may fix complement in the 
presence of syphilitic serum. Extracts of animal and human 


organs, particularly when prepared by alcoholic extraction appear to 
be distinctly more dependable than treponema extracts in the reaction 
of complement fixation. The exact nature of the substances in the 
alcoholic and in the acetone insoluble extracts is not definitely known 
except that lecithin constitutes a large part and that it is associated 
probably with other lipoids of the diaminophosphatid group, unsat- 
urated fatty acids and certain proteins or protein fractions. That 
physical conditions are of importance has been known since Wasser- 
mann's early work, for it is established that a certain degree of turbidity 
of the antigen or its dilutions is necessary. The watery extracts are in 
a state of finely-suspended colloidal emulsion and, as Reudiger and 
others have pointed out, the dilutions of the alcoholic or acetone insol- 
uble extracts by means of salt solution can be demonstrated to have an 
optimal degree of turbidity. 

The Syphilitic "Amboceptor." This is contained in the blood 
serum, the cerebro-spinal fluid and other juices of syphilitic patients and 
experimental animals. In the usual technic the blood serum is inac- 
tivated for one-half to one hour at 56 C. in order to remove comple- 
ment, but in certain modifications of the test the serum is used fresh in 
order to utilize human complement in the reaction. Bronfenbrenner, 
Reudiger and others have shown that inactivation of the serum reduces 
its fixing power. Bronfenbrenner recommends the use of unheated 
serum because of the greater delicacy of the reaction. In this way it is 
possible to use for the test 0.04 c.c. or 0.05 c.c. serum, instead of the 
usual o.i c.c. With such small amounts of serum the human comple- 
ment is a negligible factor. Long preservation or excessive heating 
of the serum may render it anti-lytic or anti-complementary. Con- 
tamination from unclean skin and glassware may make it either anti- 
lytic or lytic. The ingestion of alcohol, the presence of bile in the 
blood in jaundice or fat in the blood after a heavy meal or in cases 
of lipemia may all interfere with the activity of the fixing body in a 
syphilitic serum; sera in lipemia may be markedly anti-comple- 
mentary. There has been much discussion of the fact that human 
serum may contain natural hemolysins for sheep corpuscles. In such 
an instance the corpuscles may be dissolved by the excess of ambo- 
ceptors in spite of slight fixation of complement by the syphilitic ambo- 
ceptor, thus transforming a weakly positive into a negative reaction. 
Sasano has found, however, that the use of an excess of immune 
hemolytic amboceptor, for example, ten to twenty units and one and one- 
half units of complement, determined by careful titration does not influ- 
ence the result. Thus the factor of hemolysis by the normal anti-sheep 
amboceptor of human serum, which amboceptor is practically never pres- 
ent to the extent of more than four units, is practically negligible. 

The serum may be preserved for a considerable time if kept cool and 
in sealed ampoules or in tightly-stoppered bottles. Reudiger has found 
that mixing equal parts of fresh inactivated serum and pure sterile 
glycerol preserves the so-called syphilitic antibody for as much as 
two years. Under these circumstances the sera may become anti- 


complementary, but this property can be removed by heating to 56 C. 
for thirty minutes, and the sera are then satisfactory for use. He 
maintains that heated glycerolated sera give much stronger positive 
results than fresh unheated sera and somewhat stronger than fresh 
heated sera. This method is valuable for preserving known positive 
and negative sera as controls for the Wassermann test. 

Nature of the Syphilitic Amboceptor. The substance in the blood 
which acts as amboceptor is apparently closely related to the globulins, 
especially the euglobulin. Recently, however, Duhot has suggested that 
the albumin is of importance. Pfeiffer, Kober and Field, as well as 
Rowe, have shown an increase of globulins in syphilitic blood and 
spinal fluid. Noguchi has taken advantage of this fact in his butyric 
acid test of spinal fluid, but diseases other than syphilis may lead to 
increase of globulins in the spinal fluid. Peritz states that the lipoid 
content of syphilitic serum is increased, but Bauer and Skutezky found 
no parallel between lipoid content and Wassermann reaction. Klaus- 
ner believes that the flocculent precipitate which appears on addition 
of 0.6 c.c. distilled water to 0.2 c.c. fresh syphilitic serum is due to the 
high lipoid content of the serum. Weston has found no definite increase 
of serum cholesterol in late syphilis and no parallelism between the 
serum cholesterol content and the Wassermann reaction. According 
to Wells, " a favorite interpretation of the Wassermann reaction, which 
seems to harmonize with the facts, is that there is a precipitation of 
serum globulin by the lipoidal colloids of the antigen and adsorption of 
the complement by this precipitate." This is supported by the work 
of Jacobsthal who has demonstrated such precipitates by use of the 
ultra-microscope even when they are invisible to the naked eye. Holker 
has recently studied the colloidal phenomena and finds that the addi- 
tion of antigen to syphilitic sera produces a turbidity the curve of 
which is steeper and higher than with normal sera. He finds that the 
serum is an emulsoid and the antigen a suspensoid. Salt solution dis- 
perses the serum and precipitates the antigen, thus increasing the pro- 
tective state of the serum. Negative sera are much more protective 
than positive sera in preventing the antigen from being precipitated 
by salt solution. 

The Complement. As has been pointed out in the general discus- 
sion of complement, guinea-pig complement is most widely useful in 
immunological work. It was used by Wassermann in his original test 
and is extensively employed to-day. From the practical viewpoint it 
has certain objections. Animals are expensive and for a small number 
of tests it is undesirable to sacrifice an animal. This objection may 
be overcome by bleeding from the heart or from an ear vein (Rous), 
but the technic of both these operations is somewhat difficult. Owing 
to the lability of complement, it cannot be well preserved and the serum 
must be used soon after collection. The use of dried complement in 
filter paper has been abandoned, although such complement papers 
may be preserved for a few weeks in vacuum desiccators or in tubes 
containing calcium chloride. Drying in the frozen state in vacuo has 




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been recommended by Shakell, but Karsner and Collins found that the 
activity was lost in eleven to fifteen days. Moledzky states that com- 
plement in the frozen states retains its strength indefinitely, but Reu- 
diger found that although its strength is somewhat augmented at the 
end of one week, it deteriorates after the second week of preservation. 
Preservation for even these periods involves a good laboratory equip- 
ment and considerable skill. Kolmer recommends the addition of 
chemically pure sodium chloride to pooled guinea-pig sera in the pro- 
portion of 0.425 gram salt to 10. c.c. serum. This is effective for sev- 
eral weeks' preservation, and dilution is so adjusted as to restore the 
serum to practical isotonicity. Detre used rabbit complement, but it is 
not as desirable as guinea-pig complement and has the same objections. 
Human complement is employed in several modifications of the Was- 
sermann test, but is present in human serum in extremely variable 
amounts and is difficult to titrate. It is, however, easily accessible, 
as it is present in the serum to be tested for syphilitic amboceptor. 
The selection of the complement to be used depends to a certain 
extent upon the hemolytic system and the modification of the test 
which is employed. 

Complement should be used in accurately-determined amounts. 
Therefore, titration is of the utmost importance. Guinea-pig serum 
shows individual variation in complement, but in large laboratories 
this may be in part overcome by the " pooling " or mixing of the sera 
from several guinea-pigs. Such pooling, however, does not remove the 
necessity for titration. In some laboratories the complement is diluted 
i to 10, and the hemolytic amboceptor titrated each day by testing. 
We are of the opinion from experience and in view of the work of 
Sasano that the complement should be titrated in various dilutions 
(see page 190) against a constant amount of previously titrated hemo- 
lytic amboceptor. In either case the titration should take place on the 
same day as the Wassermann tests are made. The use of a single unit 
of complement does not allow for the presence of anti-lytic bodies in 
the reagents nor for possible deterioration of complement. At 37 C. 
the use of one and one-fourth units appears to be most satisfactory, 
whereas at ice-chest temperature the use of two units appears to be 
more desirable. Titration of the complement should be most accurate 
and the end-point be determined only by absolutely complete hemolysis. 

The Hemolytic System. Sheep erythrocytes and the correspond- 
ing hemolytic immune serum obtained from the rabbit were used by 
Wassermann and are widely used at the present time. Other systems 
include the use of goat, horse, ox, human and fowl corpuscles, with 
specific antisera obtained by immunizing rabbits. Certain investi- 
gators have depended upon the normal hemolysin for sheep erythro- 
cytes often found in human serum. This is a variable quantity and 
almost never very large. Noguchi has summarized the hemolytic sys- 
tems in a table giving all the essential data (see pages 192, 193). 

The preparation of a hemolytic immune serum has been discussed 
(see page 117). The preservation of this serum in the moist state is 


highly satisfactory if placed in amber ampoules in a refrigerator. If 
considered advisable preservatives may be added such as 0.5 per cent, 
phenol or 50 per cent, glycerol. If the serum is of high titer it may 
be preserved by desiccation, particularly if frozen and dried in a vacuum 
desiccator. Noguchi has obtained good results by drying the serum in 
filter paper. The filter paper is subsequently cut into strips and titrated 
by cutting measured lengths of the strips. We have found that this 
does not permit of sufficiently accurate titration and also that the titer 
is not well maintained. 

Preservation of Erythrpcytes. If kept in a cool place without freezing, 
sheep erythrocytes show slight hemolysis in a few days and well-marked 
hemolysis in about a week. The cells oi other animals show variable degrees 
of fragility, those of the dog being especially fragile. Various methods of 
preserving sheep erythrocytes for the Wassermann test have been studied 
by Reimann in this laboratory. The methods of particular value are preserva- 
tion with formalin (Bernstein and Kaliski) and with the solutions of Rous 
and Turner. For formalization the sheep blood is allowed to run directly 
into formalin solution in the proportion of 0.5 c.c. of 40 per cent, formaldehyde 
solution to 400 c.c. blood. The blood is then defibrinated by shaking with glass 
beads, preserved in the refrigerator and before use washed three times with 
saline for use. The method of preservation as worked out by Rous and 
Turner is carried out in the following manner: The sheep is bled directly into 
Locke's solution containing i per cent, sodium citrate, in the proportion of 
I part of blood to 4 parts of solution. The corpuscles are separated by rapid 
centrifugalization and carefully washed three times in Locke's solution containing 
0.25 per cent, gelatin. The cells are then placed in ampoules in a layer not 
more than 2 mm. in depth and covered with saccharose-Locke solution to a 
depth of about 2 cm.; the ampoules are sealed and stored at a temperature of 
5 C. to 6 C. Just prior to use the cells are washed with .85 per cent, saline 
to remove the saccharose solution, and proper dilution effected with saline. 
Strict asepsis is to be observed. 


Locke-sodium citrate solution : 

Sodium citrate 10 grams 

Sodium chloride 9-2 grams 

Sodium bicarb 0.05 gram 

Potassium chloride o.i gram 

Calcium cholride o.i gram 

Aq. dest. q.s. ad looo c.c. 

Locke-gelatin solution: 

Gelatin 2.5 grams 

Sodium chloride 9.2 grams 

Sodium bicarb 0.05 gram 

Potassium chloride o.i gram 

Calcium chloride o.i gram 

Aq. q.s. ad 1000 c.c. 

The Locke and saccharose solutions are sterilized separately and used in 
the proportion of 2.8 c.c. of the saccharose solution and 7.5 c.c. of the 
Locke's solution. 

Saccharose solution : 

Saccharose 103.0 grams 

Aq. q.s. ad 1000 c.c. 

Locke's solution: 

Sodium chloride 9-2 grams 

Sodium bicarb 0.05 gram 

Potassium chloride o.i gram 

Calcium chloride o.i gram 

Aq. q.s. ad 1000 c.c. 


Reimann found that the cells can be preserved for use in the Wassermann 
test for 3 to 4 weeks by formalization and for 21 to 25 days by the Rous and 
Turner method. " The readings obtained differ from those obtained with fresh 
cells only in so far as some sera produce slightly different results when used 
with cells from the same specimen of sheep blood." An excellent control for the 
usefulness of preserved blood is suggested by Kolmer, who maintains that there 
should be no discoloration of supernatant fluid after the second washing and 
that the blood should become brighter in color than the dark color it possesses 
after standing. 

When extreme accuracy is desired cell emulsions are made to 
contain 1,000,000,000 cells per cubic centimeter. Such emulsions are 
being more widely adopted, but many laboratories still use 5 per 
cent, or 10 per cent, emulsions calculated either from the original 
blood volume or the bulk of the centrifuged cells. The cells should 
always be most carefully washed, so as to avoid precipitin reactions 
which may appear if the serum is not entirely removed and to wash 
out antilytic substances which may appear if the blood is old. 

Influence of Temperature upon the Reaction. This influence may 
be determined as regards the velocity of the reaction and the amount 
of complement fixed. The earlier work with complement fixation was 
based on the general assumption of immunologists that a temperature 
of 37 C. represents the optimum. In 1912, however, A. McNeil pointed 
out that ice-chest temperature favors the completeness of complement 
fixation in the Wassermann test, provided the time of exposure is from 
eight to twelve hours. This was confirmed by Coca and 1'Esperance, 
Smith and W. J. McNeil, Berghausen and others, and the ice-chest 
method has now been adopted by a large number of laboratories as a 
standard method. The time, however, has been reduced to from three 
to four hours and the results appear to be entirely satisfactory. The 
antigen, serum to be tested and complement are mixed and placed in 
the ice-chest for the required time ; the mixture is then brought to about 
37 C. in a water bath, the sensitized erythrocytes added and the whole 
incubated at 37 C. for one hour. 

Dean has investigated the influence of temperature and finds that 
fixation proceeds most rapidly at 37 C. Noguchi confirms this but 
finds that at the lower temperature of 23 C., fixation will reach a maxi- 
mum but proceeds more slowly. He states that with the acetone insol- 
uble antigen " a serum containing one unit of fixing substance will 
complete the reaction within thirty minutes at 37 C., sixty minutes at 
30 C., and two hours at 23 C., irrespective of whether human or 
guinea-pig complement is used." Dean, however, finds that at o C. 
the amount of complement fixed is much greater than at 37 C., and this 
accords with experience in the use of the ice-chest method. Certain 
unknown factors may delay the action of the complement, as has been 
pointed out by McConnell, and a second incubation may accordingly 
have to be prolonged beyond the usual time. 

The Technic of the Wassermann Test. For the demonstration of the 
method we may use an alcoholic extract of ox heart as the syphilitic antigen, 
inactivated human serum from a normal individual and from a known victim 
of syphilis, guinea-pig complement and a sheep hemolytic system. 


The antigen may be made by weighing 10 grams ox heart which has been 
freed from blood, fat and connective tissue, ground in a meat grinder and dried 
under a current of air from an electric fan or in a desiccator. It is then 
extracted in 100 c.c. 95 per cent, ethyl alcohol, first by shaking 18 hours in an 
electrical shaker and then standing for 5 days at 37 C. It is filtered and kept 
tightly stoppered in an amber glass bottle in the refrigerator. For use, slowly 
add 9.0 c.c. physiologic salt solution to i.o c.c. alcoholic extract. This constitutes 
the " antigen dilution " of the charts. It must then be titrated to determine 
its antilytic properties as well as its lytic powers. The following tests of the 
antigen may be set up after previously determining the titer of the hemolytic 
amboceptor and complement. In the following titrations the complement is 
diluted so that i.o c.c. contains I unit, the amboceptor so that i.o c.c. contains 
2 units. In the first series, volume is made up by addition of salt solution, so 
that each tube contains 4.0 c.c. and in the second series so that each tube 
contains 2.0 c.c. 


Antigen dilution 





S per cent, cell 




I.O C.C. 

I unit 



2 units 

I C.C. 



0.8 c.c. 

I unit 


2 units 

I C.C. 


0.6 c.c. 

i unit 


2 units 

I C.C. 


0.4 c.c. 

I unit 


2 units 

I C.C. 




O.2 C.C. 

I unit 


2 units 

I C.C. 



I unit 


2 units 

I C.C. 





Antigen dilution 

S per cent, cell suspension 




I.O C.C. 

I C.C. 



0.8 c.c. 




0.6 c.c. 



0.4 c.c. 





In the protocols P.H. indicates partial hemolysis, C.H. complete hemolysis 
and ( ) no hemolysis. Thus it is seen that 0.6 c.c. is the smallest amount of 
antigen which is antilytic and 0.4 c.c. the largest amount which is not. For 
practical purposes one-half the latter amount, or 0.2 c.c., is the largest amount 
which may be used. This is considerably smaller than the amount of antigen 
which possesses hemolytic properties in itself, as shown in the second protocol. 

After obtaining this information, the antigen should be titrated to determine 
the smallest dose that fixes complement in the presence of a known syphilitic 
serum. A strong serum (-| I h + ) may be obtained from a laboratory or if 
not available a serum may be secured from a patient in the florid secondary 
stage of the disease. This serum is used in constant amounts of 0.2 c.c. More 
delicate titration is accomplished by the use of a known ++ serum either 
alone or in addition to the H I I h serum. Knowing that 0.2 c.c. is the largest 
dose of antigen dilution that may be employed the test is set up with that as the 
maximum amount of antigen, followed by decreasing doses. (See table on page 198.) 

The protocol includes the necessary controls, showing that neither antigen 
(12), syphilitic serum (7), nor non-syphilitic serum (19) exhibits antilytic 
powers. It shows that antigen (13), syphilitic serum (15) and non-syphilitic 
serum produce no hemolysis. It shows that non-syphilitic human serum 
(15-18) fails in the presence of the antigen to fix complement. It shows that 
in the presence of syphilitic serum the antigen solution in amounts as small as 
o.oi c.c. fixes complement. That amount, o.oi c.c., is the fixing dose and is 
doubled for the actual Wassermann test. 









5% Cell 







0.005 c.c. 


O.2 C.C. 
O.2 C.C. 
O.2 C.C. 

2 units 
2 units 
2 units 



2 units 
2 units 
2 units 

I C.C. 
I C.C. 
I C.C. 


P. H. 
C. H. 
C. H. 


2 units 


2 units 

I C.C. 


P. H. 

2 units 

I C.C. 


I C.C. 

2 units 



02 c c. 

2 units 


2 units 

I C.C. 

C. H. 

O 2 C C 



1 3 

O.2 C.C. 


I C.C. 





O.2 C.C. 
O.I C.C. 

0.05 c.c. 

O.OI C.C. 

tic human 

O.2 C.C. 
O.2 C.C. 
O.2 C.C. 
O.2 C.C. 
O.2 C.C. 

2 units 
2 units 
2 units 
2 units 
2 units 

H- 1 

2 units 
2 units 
2 units 
2 units 
2 units 


C. H. 
C. H. 
C. H. 
C. H. 
C. H. 


O.2 C.C. 


Other Reagents for the Test. The methods of obtaining guinea-pig blood, 
the hemolytic amboceptor and sheep blood have been described (see pages 
117 and 127). Various methods are in vogue for obtaining human blood. In adults 
the simplest satisfactory method is to obtain the blood by puncture of one of 
the large veins in the cubital fossa anterior to the elbow-joint. The needle should 
have a calibre of about I. m.m. and although sharp should not have an elongated 
point. The fossa is cleansed with soap and water followed by alcohol. A tourni- 
quet is applied at the middle of the upper arm and the patient instructed to 
" make a fist " several times until the veins stand out prominently. The sterile 
needle is inserted and the blood collected in amounts of 5 to 10 c.c. in a 15 c.c. 
centrifuge tube. The tourniquet is released before the needle is withdrawn 
and the wound sealed with collodion. The blood is allowed to clot, the clot 
separated from the side of the tube by means of a sterile needle, and allowed 
to contract for several hours in the refrigerator. The tube is then centrifuged 
and the serum pipetted into another tube so as to avoid hemolysis. The serum 
is inactivated at 56 to 60 C. for one-half hour before testing, unless the test 
is to be made by a modification which employs human complement. Methods 
have been suggested in which the amount of blood obtained by puncture of finger 
tip or ear lobe provides sufficient blood. In infants or obese adults blood may be 
obtained by the use of a scarifier and cupping. Bleeding from the longitudinal 
sinus, from the great toe and from the heel are also practised in infants. 

The Test. With the reagents at hand the test is set up with one or more 
antigens. In many laboratories different types of antigen are employed, as for 
example an acetone insoluble antigen, a cholesterolized alcoholic extract of 
heart muscle and a non-cholesterolized alcoholic extract of heart muscle. Others 
are employed as the operator sees fit. Antigens .may deteriorate, so that it is 
wise to have several on hand and under observation in the test. The protocol 
shows 2 antigens of the same strength. All the elements in the test are to be 
controlled to prove that they are not antilytic and to show that the hemolytic 
system operates properly. In addition it is essential to have controls with a 
known positive and a known negative serum. The antigen, complement and 
hemolysins are diluted so that the proper quantity of each is contained in i.o c.c. 
It appears to be desirable to add the human serum without dilution. This is 
done with a i.o c.c. pipette graduated in hundredths of a cubic centimeter. 
The dotted lines in the body of the protocol indicate that salt solution is to be 
substituted in quantities of i.o c.c. 



No. i 

No. 2 

Human serum 



S % cell 





2 units 

2 units 

I C.C. 




2 units 

2 units 

I C.C. 

P. H. 




2 units 

2 units 

I C.C. 




2 units 

2 units 

I C.C. 

P. H. 







2 units 

2 units 

I C.C. 




2 units 

2 units 

I C.C. 




2 units 


2 units 

I C.C. 






O. I 


2 units 


2 units 

I C.C. 






2 units 


2 units 

I C.C. 


C. H. 




2 units 


2 units 

I C.C. 


C. H. 




2 units 


2 units 

I C.C. 


C. H. 




2 units 


2 units 

I C.C. 


C. H. 



2 units 

1 I 

2 units 

I C.C. 

1 1 

C. H. 


2 units 

2 units 

I C.C. 

C. H. 


0.2 (test 

2 units 

2 units 

I C.C. 

C. H. 




0.2 (positive) 

2 units 

2 units 

I C.C. 

C. H. 



2 units 

2 units 

I C.C. 

C. H. 


2 units 

2 units 

I C.C. 

C. H. 


2 units 

I C.C. 


I C.C. 

The results of the Wassermann test are usually indicated by plus signs ; the 
following diagram indicates the interpretation of the results: 

0.2 c.c. human serum o.i c.c. human serum 





In these readings the partial hemolysis is relatively small in amount If 
with 0.2 c.c. human serum the hemolysis is well advanced without being complete 
and is complete with o.i c.c. serum, the result is indicated by the sign -f-. Other 
symbols are used, but the results are indicated in the same general way. 

Reference to the protocol shows that the serum in tubes i, 2, 3, 4 is positive 
for syphilis and would be signified as a three plus (H I h) serum. The known 
positive is a four plus (H I I h) and the known negative reacts properly. Tubes 
13 and 14 show that the antigens are not antilytic, and tubes 16, 17, 18 show that 
the sera are not antilytic. Tube 18 shows that the hemolytic system operates 
properly. Tube 19 shows that the hemolysin does not produce hemolysis with- 
out complement, and tube 20 shows that the corpuscles do not hemolyze without 
the other agents. 

The quantities given in the protocol are based on a unit of i.o c.c. to simplify 
the explanation. In order to save reagents the quantities are usually divided in 
half, so as to be on a 0.5 c.c. basis. The directions for the United States Army 
in France called for quarter quantities, so as to save reagents. The latter direc- 
tions also call for half saturation of the alcoholic heart extract with cholesterol 
(0.2 per cent.). Bronfenbrenner has suggested the use of o.i c.c. amounts of the 
reagents. Methods of measuring by drops have been employed, but are inaccurate 
because of the possible variation in the size of drops unless a stalagmometer or 
similar instrument is employed. 


Modifications of the Tests. Numerous modifications of the test 
have been recommended. These are based on variations in syphilitic 
antigen, various ways of treating the human serum, differences in 
selection of the complement and in selection of the hemo- 
lytic system. These are indicated in the chart on page 192. It 
is our opinion that any method, to be acceptable, must per- 
mit of accurate measurement of the reacting bodies. The possi- 
bilities as to methods of preparing antigen and human serum have been 
discussed. The use of human complement in the test interposes errors, 
which we believe have not been overcome. The titration of human 
complement must differ with different specimens and in the Gradwohl 
method fails to take account of the variable content of natural hemo- 
lytic amboceptor in human serum. Of the hemolytic systems recom- 
mended, the most satisfactory are the sheep or goat and the human 
systems. In most laboratories the sheep system appears to be most 
accessible and the factor of error introduced by the presence of normal 
anti-sheep amboceptors in human serum can usually be overcome by 
absorption with sheep erythrocytes or can be controlled by the use of 
one and one-half units of complement. The human hemolytic system 
largely obviates this objection, but it is sometimes difficult to obtain 
enough blood to immunize animals for the production of the specific 
immune hemolysin. We also suggest the possibility that an unusually 
strong natural iso-hemolysin in the tested serum may confuse the 
results. Kolmer, in a recent study, has found that the human hemo- 
lytic system considerably increases the delicacy of the reaction, espe- 
cially when small amounts of the patients' sera are employed. In 
positive cases he found 10 per cent, more positive reactions by the use of 
the human system than with the sheep system. 

The Specificity of the Wassermann Reaction, Numerous studies 
have been made as to the specificity of the test in the different stages 
of syphilis. In evaluating such figures certain factors of error in the 
actual performance of the test must be considered. Unless the worker 
is familiar with the many factors which may influence the reaction 
of hemolysis and the fixation of complement, as pointed out briefly 
in the chapter on hemolysis and the discussion of complement fixation, 
the results may be misleading. The type of antigen employed is also 
of significance as influencing the results. Of no small importance is 
the operator himself, for although the Wassermann test may properly 
be regarded as a physico-chemical test rather than a strictly biological 
or immunological reaction, nevertheless it requires a thorough under- 
standing of immunological procedures. Tests made in the hands of 
persons trained to perform this test, without broader training, are not 
to be given the same value as tests in the hands of broadly-trained 
immunologists. The subject of specificity of the test is closely bound 
with the clinic, in which certain factors of error in clinical diagnosis 
must be accepted. Until more satisfactory methods are provided for in 
the post-mortem room, the factor of error there is almost as large as 
in the clinic. Warthin, by particularly refined methods applied to 


cases which have been examined shortly after death, has shown the 
presence of the treponema in lesions which previously had not been 
positively known to be syphilitic. Symmers, Darlington and Bittman 
found a considerable divergence between ante-mortem Wassermann 
tests and the post-mortem evidence of syphilis, but Turnbull finds a 
striking agreement. Certainly syphilis can progress for a long time 
without gross morbid anatomical manifestations, and it seems possible 
that the pathologist cannot be sure of excluding syphilis in his ana- 
tomical diagnosis. Improved technic is the only way of reducing this 
factor of error and thereby providing an accurate control of the Was- 
sermann and other clinical tests. 

The Diagnostic Value of the Wassermann Test. Naturally this 
subject has been studied extensively and figures vary as the technic is 
improved. In 1914 Boas published an analysis of over 8000 cases 
reported in the older literature and tabulates them as follows : 

Number Positive Per - c ^ nt> 
of cases positive 

Primary syphilis 1060 629 59 

Secondary syphilis 3526 3181 90 

Tertiary syphilis 1212 1020 84.1 

Early latent syphilis 983 504 51 

Late latent syphilis 1520 605 39 

Tabes dorsalis 159 115 72 

Paresis 405 402 99.2 

These figures are sufficient to indicate that the Wassermann test is 
of distinct value in the diagnosis of syphilis. More recent statistics 
offered by Craig as the result of tests carried out by himself illustrate 
the accuracy of the reaction as applied under excellent conditions. 
In interpreting the following figures from Craig, given as the result 
of a single test on each of 4658 cases diagnosed as syphilis, it must 
be remembered that there is at least a small factor of error in the 
clinical diagnosis. The table follows: 

Number p os itive Percent, 
of cases positive 

Primary syphilis 908 813 89.5 

Secondary syphilis 1889 1817 96.1 

Tertiary syphilis 638 558 87.4 

Latent syphilis 1 173 790 67.3 

Congenital syphilis 28 25 89.2 

Parasyphilis 22 7 68.1 

4658 4010 86.2 

Tests made by Craig on 2643 individuals, either not diseased or vic- 
tims of disease other than syphilis, showed the reaction to be positive in 
eleven instances (0.4 per cent.). These eleven instances included four 
cases of malaria, three of tuberculosis (two of which ultimately gave a 
clinical history of syphilis), three cases of pityriasis rosea and one case 
in which the diagnosis was not established. It is to be considered pos- 
sible that diseases other than syphilis may produce those changes in the 
blood which lead to fixation of syphilitic antigen and complement; 
among these are occasional cases of leprosy, scarlatina, malaria, try- 


panosomiasis and certain skin diseases. Gordon, Thomson and Mills 
have recently insisted that malaria will not produce a positive re- 
action unless complicated by syphilis or as the result of faulty technic. 
Although a controversial point, we believe that occasional cases of 
tuberculosis may give a positive Wassermann test. That this is not 
necessarily due to coincident infection with syphilis is shown by the 
experience of Petroff, who found a positive Wassermann in a 
tuberculous cow. 

Interpretation of Results. Craig and others are of the opinion that 
a strongly positive result, such as would be indicated by -| | | |- in 
our schedule, is conclusive evidence of syphilis, whether there are 
symptoms or not. Other degrees of fixation must be interpreted with 
the aid of clinical history and symptoms. A single negative reaction 
does not exclude syphilis. In doubtful cases the so-called provocative 
treatment should be applied. This means that a short course of mer- 
cury or preferably half the usual dose of salvarsan or neosalvarsan 
should be given and the Wassermann test made subsequently. It is 
advisable to test the blood twelve, and twenty-four hours after pro- 
vocative administration of salvarsan as well as every day for at least 
ten days. If the reaction is to become positive, it usually does so in 
from a few hours to five or six days, but may be delayed for ten days 
or even more. That this is an absolutely specific effect of the drug is 
contradicted by the report of Wildgren, who found that the injection 
of milk may produce similar results. Endless discussion might be pre- 
sented as to the interpretation of the Wassermann test in the clinical 
diagnosis of syphilis, but we incline to the view that this test, as is 
true of many laboratory examinations, is to be regarded as important 
evidence in clinical diagnosis, is of striking specificity when properly 
performed, but is not absolutely pathognomonic. 

Dependability of the Test. Criticism has been directed against 
the test because of the fact that results do not always agree with 
clinical findings and because of differences in results upon the same 
serum in different laboratories. It must be admitted that the factors 
of error in the test are greater than in clinical diagnosis of the disease. 
Discrepancies in reports from different laboratories may, in part, be 
due to inherent faults in the test, to faults in technic, to faults in selec- 
tion of materials and to insufficient training of the worker. The older 
literature contains serious criticisms of the test, as for example the 
papers of Wolbart and of Uhle and Mackinney. Under the direction 
of the Medical Research Committee of Great Britain in 1918 the results 
obtained independently by Dr. C. H. Browning, Dr. J. Mclntosh and 
Col. L. W. Harrison upon the same specimens are in very close agree- 
ment. More recently Solomon has analyzed the results of 3000 tests 
carried out in two different laboratories by skilled workers, Dr. Hinton 
and Dr. Castleman. There was complete agreement of results in 93.44 
per cent, of this large series of tests. This study demonstrates that 
with modern methods and skillful performance of the test results are 
highly dependable. 


Quantitative Results with the Wassermann Test. For various 
purposes, more particularly the observation of the results of treatment, 
it may be desirable to titrate accurately the amount of patient's serum 
which serves as an amboceptor. This may be done by using different 
quantities of the serum. Dilutions of the serum are made with salt 
solution, i to 4, i to 8, i to 16, i to 32, i to 64, or are measured as 
o.i c.c., 0.05 c.c., 0.03 c.c., 0.02 c.c., o.oi c.c., etc. The tubes are treated 

in the usual fashion and the results recorded as-g-, indicating complete 

fixation in dilution I to 8, -^ indicating partial fixation in dilutions of 


i to 1 6, indicating hemolysis or no fixation in dilutions of i to 32. 

Wassermann Test on Spinal Fluid. Spinal fluids are not inac- 
tivated and are employed in larger volumes than blood serum, up to as 
much as i.o c.c. Hauptmann and Hossli were the first to insist upon 
the use of large quantities of spinal fluid, and this modification changed 
the entire conception of the frequency of positive results in the spinal 
fluid of such diseases as paresis and tabes dorsalis. The test with spinal 
fluid is of particular value in syphilis of the central nervous system, 
where it is somewhat more specific than the test with blood serum. 
The test has also been used with success with transudates and exudates 
from the peritoneum, pleura and pericardium. Apparently of value 
in examination of the spinal fluid is the Lange colloidal gold test, 
described in texts of clinical pathology. 

Post-mortem Wassermann Tests. In a certain number of cases, 
death ensues too soon after the patient comes under observation to 
secure blood for the Wassermann test. Not infrequently the result of 
a Wassermann test may aid the pathologist in morbid anatomical diag- 
nosis and may furnish information of value to the clinician in the con- 
sideration of doubtful cases. The question arises as to whether or not 
post-mortem changes in the blood will invalidate the Wassermann test. 
Valuable information has been collected by Graves. In a series of 
400 cases he found that only 0.46 per cent, of sera from cadavers were 
antilytic and only 0.58 per cent, of sera were hemolyzed, coagulated 
or otherwise unfit for use. The post-mortem and ante-mortem results 
were the same in 97 per cent, of sixty-eight controlled cases. " The 
reactions conformed to the anatomic and historical evidence in 304 of 
378 cases, or 80.4 per cent." Contradictory findings are recorded in 
less recent literature, but we believe that valuable results may be ob- 
tained with blood taken after death. 


The advantage of a complement-fixation test in the diagnosis of 
early pulmonary tuberculosis and in concealed or suspicious lesions is 
obvious. Certain authors, Craig, Miller, von Wedel, report a high 
percentage of positive reactions in tuberculous individuals, whereas 
others, Cooper and Lange, report relatively few positive results. Petroff 
is of the opinion that these differences may be due to lack of complete 


and careful study of the cases clinically, as well as a failure to observe 
minute details of the test. 

Antigens are of the utmost importance, and numerous forms have 
been suggested. There appears to be well-founded evidence for using 
several strains of the human type bacillus associated with one or more 
strains of bovine type. The methods of making antigen vary and 
include the use of saline suspensions or extracts of tubercle bacilli, 
living or dead, intact or pulverized ; filtrates of broth cultures ; ether 
alcohol extracts of whole or autolyzed bacilli, and extracts of tubercu- 
lous organs. Apparently those extracts which contain both lipoids and 
proteins are most satisfactory. The antigenic substance is thermostable. 

The human serum is inactivated, and in PetrofF s hands appears to 
be most satisfactory if collected one or two days before the test. 
Accurate titration of complement, to be used in doses of two units, 
and of hemolytic amboceptor is essential. Guinea-pig complement and 
a sheep-rabbit hemolytic system are satisfactory. It is absolutely essen- 
tial that glassware be perfectly clean and that measurements be accur- 
ate. The incubation of the mixture of antigen, tuberculous amboceptor 
and complement should be from one and one-half to two hours at the 
optimal temperature of 35-4O. 

Wilson, using a lipoid-free bacillary antigen, attaches great im- 
portance to the complement and finds that there is not a universal 
adaptability of guinea-pig complement. That from some guinea-pigs 
appears to be fixed more readily than that from others. Therefore, in 
general, pooled complements are likely to give the best results. If a 
single complement is used tests should be made to determine the extent 
of fixation. Von Wedel states that preservation of the patient's serum 
in the ice-box for five to seven days favors the reaction, but Petroff 
found that fresher sera are preferable. It is desirable to make several 
tests at intervals upon the same patient. As the result of 1555 tests on 
713 cases Petroff obtained the following results: 

Cases Positive Negative Percent. 

Clinically active tuberculous 212 199 13 93.9 

Quiescent tuberculous 158 89 69 56.3 

Apparently cured more than two years 58 5 53 8.5 

Normals 78 3 75 3.8 

Suspected 166 65 101 39.1 

Other diseases 41 6 35 14.6 

An analysis of these figures shows that under proper conditions 
complement fixation is of distinct value in the diagnosis and prognosis 
of tuberculosis. Basing his conclusions on experimental data Petroff 
considers " the complement-fixation test in tuberculosis more specific 
than the Wassermann test " in syphilis, an opinion in which we concur. 
Nevertheless, its most ardent advocates do not regard the test as pathog- 
nomonic and Petroff regards it as " only one of the many links in the 
tuberculosis diagnostic chain." It is unfortunate that the complement- 
fixation test gives the highest percentage of positive results in cases in 
which the need for such diagnostic aid is least evident, namely in those 


cases of active tuberculosis in which the diagnosis on clinical and 
bacteriological grounds is reasonably certain. 

"Acid-Fast Fixation." Of great interest is the fact as shown by 
Cooke and others that the complement-fixation test affirms the close 
biological relationship of the acid-fast bacilli. From rabbits immunized 
with various acid-fast bacilli Cooke obtained sera which reacted inter- 
changeably with each member of the group employed in the experiment. 
In certain instances the immune sera reacted somewhat more strongly 
with their own antigenic organism than with others of the group. Cooke 
also found that the sera of tuberculous patients react not only with 
the tubercle bacillus but also with other acid-fast bacteria. Sera from 
cases of leprosy also contain complement-binding substances which 
react with antigens made from several members of the acid-fast group, 
the cases of nodular leprosy giving more striking fixation than those 
of anesthetic type. According to Cooke, the Wassermann test gives 
crossed reactions in tuberculosis which are too frequent to be ex- 
plained by the coincidence of syphilis. 


As with other immune reactions of the animal body, time plays an 
important part in the production of complement-fixing bodies in gono- 
coccal infections. Acute gonorrhea is usually diagnosed with ease 
by bacteriological methods, but it is not until the disease has persisted 
several weeks that complement-fixing bodies are likely to be demon- 
strated. The value of complement fixation appears in those cases where 
simpler bacteriological methods are not adaptable, such as gonorrheal 
rheumatism and endocarditis, as well as infections of deeper parts of 
the genital tract, such as the Fallopian tube, Cowper's glands and 
prostate. The test is also useful in determining the cure of the disease. 

Muller and Oppenheim in 1906 reported favorable results with the 
gonococcus complement-fixation test. Bruck and subsequently 
Meakins had a similar experience, but more recent study indicates 
that the older methods possess little specificity. The work of Teague 
and Torrey, Wollstein, Watabiki and Schwartz and McNeil demon- 
strated the occurrence of numerous immunologically distinct forms of 
gonococcus and the necessity for using several strains in the antigen. 
It now appears that from ten to fourteen strains are desirable. 

The production of antigen has been extensively studied. Salt 
solution extracts appear to be satisfactory. Alcohol extracts have no 
value, and Wilson believes that a lipoid-free antigen presents an im- 
provement in titer, stability and freedom from anti-complementary 
activity. Warden claims good results with an antigen composed of 
salts of the fats of the gonococci. Thomson, working under the direc- 
tion of Col. L. W. Harrison, reports excellent results by dissolving 
the organisms in decinormal sodium hydrate solution and restoring 
to the neutral point by decinormal hydrochloric acid. In the hands of 
most workers the sheep-rabbit hemolytic system appears to be satis- 


factory, but it has the same objections as obtain in the Wassermann 
test. A human-rabbit .system may be substituted if desired. 

The test appears to be highly specific and of great clinical value 
when properly performed Although the gonococcus and meningo- 
coccus are closely-related organisms and may, according to Wollstein, 
give crossed complement-fixation reactions there is no satisfactory 
evidence that epidemic cerebrospinal meningitis in man produces con- 
fusing complement-fixing bodies. Dixon has recently studied 840 
tests made by Dixon and Priestly on 625 individuals. Of fifty-three 
strongly positive reactions 90.4 per cent, had gonorrhea or a history 
of the disease, of sixty-six moderately strong reactions 86.3 per cent, 
were confirmed clinically, of seventy-five weakly positive reactions 72 
per cent, were confirmed clinically, of ninety doubtful reactions 58.9 
per cent, were clinically cases of gonorrhea. Of 341 negative reactions 
26.1 per cent, were cases of gonorrhea in some form; of these only 
one case was positive to a second test. Therefore, a positive test is 
to be regarded as strong presumptive evidence of the disease, but 
both positive and negative reactions should be controlled by sub- 
sequent tests. 


Glanders. The complement-fixation test in this disease appears 
to be highly specific independently of the strain of the antigenic 
organism. Its principal application is in the disease as it affects horses. 
The mallein test and the agglutination test are satisfactory but can be 
supplemented by complement fixation. Occasionally it may be ser- 
viceable in human medicine. 

Typhoid Fever. Although earlier workers obtained variable re- 
sults, later investigations in the hands of Garbat and of Kolmer with 
salt solution extracts of numerous strains of the bacillus, the so-called 
polyvalent antigen, have given excellent results more particularly in 
the second or third week of the disease or later. Blood cultures, the 
Widal and the Dreyer tests are so much more easily performed that 
the complement-fixation test is to be regarded as only supplementary. 
Nevertheless, complement fixation is more likely to occur in the course 
of the disease than as the result of prophylactic vaccination and accord- 
ingly may gain diagnostic value. 

Smallpox. Positive results have been obtained in this disease by 
Jobling, Sugai, Dalm, Klein, Kolmer and others. The antigen has been 
obtained either from the lesions of vaccinia in calves or from human 
smallpox lesions. Salt solution extracts appear to be better than alcoholic 
extracts. In addition to the diagnostic value, the reaction adds to the 
evidence concerning the biological identity of smallpox (variola) vari- 
oloid and vaccinia. Our interpretation of Xylander's results indicates 
that vaccinia in man does not lead to the establishment of complement- 
fixing bodies over a long period of time and therefore in all probability 
is not a true index of immunity to smallpox. The great diagnostic 


value lies in the differentiation of smallpox from syphilis and from 
chicken-pox (varicella). 

Whooping-Cough. With antigens made from the pertussis bacil- 
lus of Bordet-Gengou the reaction appears to have considerable diag- 
nostic value. 

Echinococcus Cyst. The antigen is obtained by filtering the cyst 
fluid of man or sheep and preserving with 0.5 per cent, phenol in a cool 
place. Varying results have been reported, but the test appears to be 
worthy of further investigation where material can be obtained for 
its use. 

Malignant Tumors. Numerous attempts have been made to aid 
in the diagnosis of malignant tumors by the complement-fixation test, 
using antigens prepared from tumor material. The results have been 
conflicting. Von Dungern has devised a test using, on empirical 
grounds, an antigen prepared by making an acetone extract of normal 
human red blood-cells. He has obtained fixation in as high as 90 per 
cent, of known cases of malignant tumors. The test, however, has not 
as yet been sufficiently widely applied to justify recommending it as 
of clinical value. 

Sporotrichosis. Widal, Abrami, Joltrain and Weil have obtained 
excellent results using as antigen the sporotrichum Beurmanni. Moore 
and Davis have recently demonstrated fixation with a human serum in 
the presence of Schenck-Hektoen, Beurmann and Davis strains of 
the organism. This reaction, in addition to agglutination, is of distinct 
diagnostic value. 







Definition. On casual consideration hypersusceptibility appears to 
be a condition exactly the opposite of immunity. If by immunization 
an animal becomes more than normally resistant to a poisonous or in- 
fective agent so in the state of hypersusceptibility it is more than nor- 
mally susceptible to poisons, to infective agents and to agents which in 
the normal animal appear to be entirely innocuous. More critical 
examination of the phenomenon, however, has led to the conception 
that hypersusceptibility is but one manifestation of the intricate 
mechanism of immunity. The reasons for this latter conception will 
appear in the subsequent discussion. The term hypersusceptibility is 
not to be confused with anaphylaxis, with which, in our judgment, it 
is not synonymous. We prefer to limit the term anaphylaxis to that 
state of hypersusceptibility to a given substance which has been induced 
by a previous injection of the same substance. The reaction is limited 
to proteins or protein fractions. Natural hypersusceptibility to non- 
protein substances may occur, but this condition cannot be induced by 
a previous administration of such substances. 

Occurrence. Hypersusceptibility may be natural or acquired. 
Undoubtedly certain individuals in whom the condition is supposed to 
be natural have acquired the state by preliminary inoculation of the 
substance to which they are susceptible. This may be an unconscious, 
forgotten or concealed acquisition. The introduction of practically any 
protein into the tissues of the body may lead to the acquisition of a 
hypersusceptibility of long duration unless the primary inoculation is 
succeeded by others at proper intervals and in proper amounts to produce 


immunity. In man natural hypersusceptibilities are believed to be 
manifested upon the introduction of the special proteins or similar sub- 
stances into the respiratory tract, the alimentary canal, into the skin and 
by injection into the tissues, body spaces or circulation. Man may 
exhibit respiratory symptoms in the presence of vegetable effluvia, as in 
" hay fever," " rose fever," and of the effluvia of certain animals, such 
as the horse and guinea-pig. In individuals thus susceptible, local or 
general reactions may occur following inoculation with the specific 
animal or vegetable protein. The ingestion of animal proteins, such as 
egg, or vegetable proteins, such as strawberry, may produce severe 
gastro-intestinal disturbances sometimes accompanied by general symp- 
toms. In certain cases this hypersusceptibility may have been acquired 
by previous sensitization, but in the greater number no such explanation 
is to be offered. In babies susceptible to egg-white there is no prob- 
ability that preliminary direct sensitization occurs, but it is possible 
that the tendency to hypersusceptibility may have been inherited. The 
instances mentioned are examples of individual hypersusceptibility. 
Although less clear cut there are also evidences of species hypersuscepti- 
bility, as, for example, the fact that ox serum is distinctly toxic for 
guinea-pigs and much less so for man. The acquired forms of 
hypersusceptibility will be considered under the general discussion 
of anaphylaxis. 

Anaphylaxis. Following the introduction of the serum treatment 
of disease, disturbing elements appeared, the most striking of which 
were the frequent production of " serum rashes " and the reports of 
occasional severe constitutional reactions and even sudden death. Von 
Pirquet and Schick pointed out on the basis of a clinical investigation 
in connection with the serum treatment of diphtheria and scarlatina, 
that in from seven to twelve days following a single injection of serum 
or several injections on successive days, a so-called " serum disease " 
appears. This is characterized by macular or maculo-papular eruptions 
of urticarial type, malaise, fever and other symptoms. After this period 
a subsequent injection of the same protein leads to the appearance of 
similar symptoms and signs usually within twenty-four hours. After 
the lapse of months or years the reaction may be delayed and fail to 
appear for several days, but is only rarely as late as that following the 
primary injection. In other words, the patients appeared to have been 
sensitized by the primary injection. Not being able to define exactly 
the nature of this condition, the name allergy was suggested, indicating 
an " altered state " of the animal body. The usage of the term at the 
present time is confusing and definitions vary ; we, therefore, prefer not 
to employ it. 

Experimentally similar phenomena had been noted in the course of 
other studies as far back as Magendie in 1839, but it remained for 
Richet and Portier in 1902 to point out the fact that an animal may be 
rendered hypersusceptible to a poison, by the previous injection of a 
small dose. They used actino-congestine, a toxic , protein extracted 
from the tentacles of actinia. Because the phenomenon indicates a 


condition the opposite of prophylaxis they named it anaphylaxis. As 
a result of the reports of accidents following the use of diphtheria 
antitoxin, Rosenau and Anderson investigated the problem experi- 
mentally and found that the danger lies in the serum rather than in its 
content of antitoxin. They demonstrated that the reaction is specific 
for the protein employed, that the period of " incubation " is about six 
days and that once established the sensitive state persists for many 
months with but slight reduction in intensity. In the same year, 1906, 
Otto entirely independently published similar findings in Ehrlich's 
laboratory as the result of an interview between Ehrlich and Theobald 
Smith. Smith had noted that animals used for the titration of diph- 
theria antitoxin were subsequently extremely sensitive to horse serum. 
Otto, accordingly, employed the name Theobald Smith phenomenon. 
Of somewhat similar significance, but for the time without the same 
direct application to medicine, were the investigations of Arthus, who 
in 1903 published a study in which he showed that if repeated sub- 
cutaneous injections of protein are given, the fourth and subsequent 
injections may lead to severe local reactions which may go on to 
gangrene. If a later injection is given intravenously death may result. 
Arthus also recognized the specificity of the reaction. The year 1906 
marked the beginning of a period of widespread investigation 
of anaphylaxis. Much has been learned in regard to the mechanism 
of the process, but the fundamental principles are still in the form 
of hypotheses. 

The Sensitization. The substances necessary for the demonstra- 
tion of anaphylaxis are proteins. These need not contain all the amino- 
acids, for Wells has shown that certain vegetable proteins, zein, hordein, 
gliadin, lacking " one or more such amino-acids as glycocoll, tryptophane 
or leucine produce typical reactions " and Abderhalden claims to have 
demonstrated anaphylaxis with a compound polypeptid made up of four- 
teen amino-acid molecules, which include only two of the amino-acids, 
leucine and glycocoll. The sensitizing substance is extremely thermo- 
resistant. Wells finds that proteins such as casein and ovo-mucin 
which are not heat coagulable are active after heating to 100 C. and 
Besredka has found that if a coagulable protein is so diluted as to 
prevent coagulation it withstands temperatures up to 120 C. Rosenau 
and Anderson found that if the protein be in the dry state it may be 
heated to 170 C. for ten minutes and upon re-solution will serve for 
the production of anaphylaxis. Heat or chemical agents which render 
the protein insoluble destroy its sensitizing properties. Trypsin diges- 
tion has the same effect. Gay and Adler reported that upon frac- 
tioning serum with ammonium sulphate the euglobulin contains the 
sensitizing substance, but not that substance which intoxicates at the sec- 
ond injection. Kato, however, finds that the globulins possess the largest 
content of both sensitizing and intoxicating substances. Bogolomez 
and subsequently Meyer claimed that anaphylaxis could be produced 
with lipoids but this has failed of confirmation in the hands of Wilson 
and of White and others ; it is not generally accepted. The chief dif- 


ficulty in the work with lipoids lies in the fact that it is practically 
impossible to obtain the lipoids in pure form ; an extremely small amount 
of adsorbed protein may produce the reaction. 

The method of sensitization is by parenteral routes, although 
Rosenau and Anderson in their original communication state that they 
had been able to sensitize guinea-pigs by feeding horse serum. Bes- 
redka was unable to confirm this, but in a few dogs we have obtained 
results which have been highly suggestive. A question of fundamen- 
tal importance in this connection is whether or not proteins may be 
absorbed through an intact intestinal mucosa without digestion. Ac- 
cording to the work of Van Alstyne and Grant, such absorption may 
occur. Absorption of the whole protein through the intestinal mucosa 
or the mucosa of other surfaces might well serve to sensitize animals 
or man, but as yet the problem is not conclusively settled. If 
the inoculation be by parenteral routes there is apparently little 
difference in outcome whether administered subcutaneously, intra- 
venously or intraperitoneally. 

The amount of protein necessary for sensitization is extremely 
small. In their original work, Rosenau and Anderson found that in 
guinea-pigs 0.000,001 c.c. horse serum suffices. Wells succeeded in 
sensitizing guinea-pigs with 0.000,000,05 gram crystallized egg albumin. 
Larger sensitizing doses are necessary in order to produce subsequent 
death from anaphylactic shock. Such minute doses are not applicable 
in the case of rabbits, dogs and monkeys, in which it may be necessary 
to inject the material on two or three successive days in order to 
sensitize. The minimal sensitizing dose in man is not known. In 
experimental animals there is an optimal sensitizing dose which bears 
a certain relation to the subsequent intoxicating dose, as has been shown 
by White and Avery. In a general way, the smaller the sensitizing 
dose, the larger the minimum intoxicating dose and vice versa, but a 
sensitizing dose may be too large for satisfactory sensitization. Accord- 
ing to Besredka the larger doses also require a longer time for sensi- 
tization to appear. 

Period of Incubation. For a period of eight to twelve days after 
the sensitizing dose, subsequent injections of the same material produce 
no evidence of hypersusceptibility. Gay and Adler reported that if the 
euglobulins of serum are employed for sensitizing, the period of incu- 
bation may be shortened to four or five days. If during this period 
a second injection be given the animal is more likely to become immune 
than hypersusceptible. Rosenau and Anderson found that the state 
of hypersusceptibility increases until the twenty-first day, after which 
it very gradually diminishes but persists in modified form probably 
throughout the life of the animal. 

Intoxicating Injection. The French term, injection dechainante, 
is highly descriptive of this part of the process, as it indicates the 
explosive character of the manifestations that are likely to occur. This 
injection may be intravenous, intrameningeal, intraperitoneal or sub- 
cutaneous. The rapidity of reaction and severity of symptoms are most 


marked in intravenous injection and exhibit decreasing severity in the 
order named. Besredka estimates that by the use of serum, approxi- 
mately equivalent reactions may be produced by intravenous injections 
of 0.05 to o.i c.c., intrathecal injections of 0.066 to 0.125 c.c. and intra- 
peritoneal injections of 5.0 to 6.0 c.c. Subcutaneous injections in experi- 
mental animals rarely produce severe or fatal reactions. 

When used for the intoxicating dose the proteins are subject to the 
same physical and chemical agents as have been discussed in connec- 
tion with the sensitizing injection. The statement of Gay and Adler 
that the sensitizing agent is contained in the globulin fraction of serum 
and the intoxicating agent in the whole serum and albumin fractions 
is not generally accepted and has recently been contradicted by Kato. 
Kato found that guinea-pigs sensitized to any of the serum fractions 
respond to intoxicating doses of any of the fractions but most strongly 
to that fraction to which they were sensitized. The aging of serum 
has an important influence. The toxicity of fresh serum decreases 
rapidly during the first ten days of preservation to about half its 
original power. A slight decrease occurs during the first two 
months, after which the deterioration is extremely gradual. Besredka 
has found that a serum twenty years old produced anaphylactic shock 
in a sensitized animal. Uhlenhuth states that he has produced ana- 
phylactic shock with proteins from mummies. 

The selection of the route of intoxicating injection depends on the 
character of the protein; the intravenous route is undesirable with 
solid proteins and even with bacteria because thrombosis and embolism 
confuse the picture of anaphylaxis. The minimal intoxicating dose is 
larger than the minimal sensitizing dose in the ratio of about 100 to I. 
Wells has obtained fatal reactions with 0.000,001 gram crystallized 
egg-white. Fatal reactions are rarely obtained with less than 0.025 c.c. 
serum and, as a rule, 0.05 c.c. to o.i c.c. is required. We find that for 
laboratory demonstrations the use of 0.05 c.c. serum given subcu- 
taneously for sensitization and o.i c.c. fresh serum given intravenously 
practically always produces fatal reactions. Of great importance is the 
fact that there is considerable individual variation not only in the 
sensitivity of the experimental animals but also in the sera employed 
for experiments. Wells has stated that blood serum contains so many 
substances that it is in reality an " extract of the animal " ; hence 
variations such as are found in serum are not present in pure iso- 
lated proteins. 

The Reaction. The phenomena of the reaction may be discussed 
under three heads, the objective manifestations, the morbid anatomical 
changes and the functional disturbances. The reaction may be imme- 
diate or delayed, depending upon the sensitiveness of the animal, the 
size and mode of administration of the toxic dose and the state of 
deterioration of the intoxicating substance. The immediate reaction 
is called anaphylactic shock. In the guinea-pig the objective manifesta- 
tions include rubbing of the nose, ruffling of the fur, evacuation of 
urine and feces, spasmodic movements of increasing severity, including 


Drawing of the gross appearance of the lungs of the 
guinea-pig in anaphylactic shock, showing marked 
distention and pallor. Note the overlapping of the 
lobes and the almost complete masking of the heart. 


violent general convulsions, marked inspiratory and expiratory effort 
with cyanosis, exhaustion and death from respiratory failure with the 
heart still beating. In the dog the respiratory and convulsive phe- 
nomena are not so marked ; there is violent precordial activity, marked 
fall in blood-pressure, diarrhea and vomiting. In man the phenomenon 
may show predominance of the respiratory and convulsive symptoms 
or of the cardio-vascular and the gastro-intestinal symptoms. Other 
animals show variations of the general picture outlined. The necropsy 
on a guinea-pig shows large, pale, distended lungs filling the thoracic 
cavity, cardiac dilatation, particularly of the right side, passive con- 
gestion of the abdominal viscera sometimes associated with minute 
hemorrhages in the gastro-intestinal tract. The lungs may show con- 
gestion, edema and small hemorrhages, but, as a rule, the distention 
is so marked that there is little blood in these organs. Microscopically 
there is marked distention of the alveoli, with rupture of their walls, 
constriction of the bronchioles and frequently of the small arteries. 
Gay and Southard describe fatty degenerative changes in capillary 
endothelium near small hemorrhages, as well as fatty changes in heart 
muscle, skeletal muscle and peripheral nerves. Beneke and Stein- 
schneider found Zenker's degeneration particularly of the respiratory 
muscles, but Wells believes this to be the result of asphyxia which pro- 
duces Zenker's hyalin through the increase of lactic acid in the muscle. 
In dogs and other animals the pulmonary distention is not marked ; the 
important features are dilation of the heart, marked congestion and 
multiple hemorrhages. None of these anatomical changes is charac- 
teristic or to be distinguished from other toxic conditions. The pul- 
monary distention is more distinctive than any of the other changes. 

From the functional point of view there have been extensive in- 
vestigations of the distention of the lungs, the fall of blood-pressure, 
fall in temperature, delayed coagulability of the blood and alterations 
of the nitrogen metabolism. Auer and Lewis found that in guinea-pigs 
death is due to asphyxia " apparently produced by tetanic contraction 
of the smooth muscles of the bronchioles." This is independent of 
pithing, section or degeneration of the vagus, and is therefore periph- 
eral, either in the nerve terminals or the muscle itself. Auer has 
shown that atropin reduces this effect, thus indicating the action upon 
nerve terminals. Karsner and Nutt found that there is a definite 
quantitative relation between the intoxicating dose of serum and the 
protective dose of atropin and this fact, together with the protective 
action of anesthetics such as ether, indicates that there may be factors 
involved other than mere physiological antagonisms. The exciting 
action on smooth muscle is not confined to the bronchiolar muscle for 
Schultz demonstrated a similar action in vitro on smooth muscle of the 
intestine and bladder of sensitized guinea-pigs and this has subsequently 
been extended to include other smooth muscle such as uterus. Pelz 
and Jackson have recently observed broncho-constriction in dogs during 
the acute shock, but although this is severe we have been unable to 
demonstrate acute emphysema in dogs. 


The fall in blood-pressure appears in anaphylactic shock in the dog 
and cat but is not so highly characteristic of the reaction in the guinea- 
pig or rabbit. Biedl and Kraus described the condition, and it has 
since been studied extensively. Pearce and Eisenbrey note that it 
amounts to a fall of from 20 to 30 mm. mercury in the dog and believe 
it to be due to vaso-dilatation, particularly of the splanchnic area, due 
to action upon the nerve endings rather than upon the muscle. Schultz 
was of the opinion that the fall in pressure is due to direct action upon 
the heart by the toxic agent. He expressed the opinion that in the cat 
the fall in general pressure is due to vaso-constriction in the pulmonary 
circuit so that the right heart cannot empty itself. Eisenbrey and 
Pearce in a further study on dogs found that the functional activity 
of the myocardium is not primarily affected, that there is no satisfactory 
evidence of pulmonary vaso-constriction and that the later changes 
in the myocardium with the fall in general pressure result from incom-. 
plete filling of the heart consequent on the accumulation of blood in 
the larger venous trunks, particularly of the splanchnic area. Simonds 
finds that with the fall in arterial pressure, there is a fall in pressure in 
the superior vena cava and a rise in portal vein pressure, associated 
with an increase in the volume of the liver. Upon examination of the 
hepatic vein of the dog the vessel shows a very heavy musculature as 
compared with that of the herbivorous animals, and Simonds con- 
cludes that spasm of the hepatic vein and its tributaries explains the 
phenomena observed. Manwaring and subsequently Voegtlin and 
Bernheim had previously found that exclusion of the liver from the 
circulation prevented the appearance of anaphylactic shock, observations 
well in accord with Simonds' hypothesis. However, Pelz and Jackson 
excluded the entire abdominal circulation, and in spite of this demon- 
strated broncho-constriction and marked fall in blood-pressure. Thus, 
although numerous factors may play a part, the only fact that we can 
bring forward as generally accepted is that the fall in arterial pressure 
is associated with peripheral vaso-dilatation. Davis and Petersen 
observed an increase in the volume of lymph for a short time imme- 
diately following injection and again for a longer period beginning 
about one hour after injection. The antiferment increases in the lymph 
without any change in the blood serum. 

There can be no doubt that the gaseous interchange in the 
convulsive phases of anaphylactic shock is increased. Varying reports, 
however, have appeared as to the influence of anaphylactic shock upon 
nitrogen metabolism. Major found an inconstant decrease of nitrogen 
output in rabbits during shock, but this increased in the animals that 
survived the immediate shock to such a degree as to exceed the intake. 
Zunz and Gyorgy found a definite increase in amino-acids, which 
Jobling, Petersen and Eggstein confirmed, with the additional informa- 
tion that the total non-coagulable nitrogen is increased. Hisanobu 
found a marked increase of urea nitrogen, as well as of the non-urea 
and amino-acid nitrogen. He concludes, as would also be apparent 
from Major's work, that there is an abnormally rapid destruction of 


FIG. 17. Drawing of the microscopical appearance of the lung of the guinea-pig 
in anaphylactic shock, showing the alveolar emphysema, constriction of the bron- 
chioles and of an arteriole. 


tissue proteins. Jobling, Petersen and Eggstein found an increase in 
non-specific protease with a decrease of antiferment and an associated 
decrease of serum proteoses ; this is followed by a progressive increase 
in non-coagulable nitrogen, proteoses and serum lipase. They, there- 
fore, conclude that " the acute intoxication is brought about by the 
cleavage of serum proteins (and proteoses) through the peptone stage 
by a non-specific protease." Modern opinion thus favors an increase 
in nitrogenous metabolism in anaphylactic shock and this may well 
be due to a liberation or mobilization of proteases ; that the action of 
the latter is limited to the blood appears to us not to be conclusively 
proven. In spite of the increase in metabolism there is a fall in body 
temperature; therefore, there must be an increase in heat radiation. 
In lower animals the respiratory function is of great importance in heat 
radiation, and we suggest that the marked increase of respiration in 
anaphylactic shock has some bearing on this problem, but we by 
no means wish to exclude other factors that may play a part in 
the phenomenon. 

The decrease in coagulability of the blood was first observed by 
Biedl and Kraus and since has been amply confirmed. They believed 
the change to be due to either a decrease of thromboplastin or an 
increase in antithrombin. The salts of the blood apparently are un- 
changed. Achard and Aynaud, as well as Lee and Vincent, found 
a decrease in the number of platelets, but this was not found by Biedl 
and Kraus. Shattuck found a delay in action of prothrombin. Pepper 
and Krumbhaar reached the same conclusion as Biedl and Kraus con- 
cerning a decrease of thromboplastin or an increase of antithrombin. 
Bulger concludes, in terms which summarize our knowledge at the 
present time, that the decrease in coagulability is " due to changes in 
that stage of the coagulation process at which thrombin is formed 
through the interaction of prothrombin, calcium, thromboplastin 
and antithrombin ( ?) . These changes are probably due to variations 
in thromboplastin." 

Desensitization or Anti-anaphylaxis. If an animal recovers from 
anaphylactic shock its earlier hypersusceptibility is replaced by a period 
of resistance during which injections of the specific protein produce no 
demonstrable reaction. This refractory period lasts for a varying 
period of time up to several weeks, and although the animal subse- 
quently becomes hypersusceptible, it rarely reaches the same degree of 
hypersusceptibility which it primarily exhibited. These facts were 
pointed out in the original investigations of Rosenau and Anderson 
and of Otto. Besredka has studied the matter extensively and has 
found that very small doses of the protein may desensitize, doses in 
themselves too small to lead to any observable symptoms. By repeated 
injections it is possible to produce such a degree of resistance that the 
animal may withstand doses 1000 times as great as that which proves 
fatal if desensitization has not occurred. The rapidity with which 
desensitization appears depends upon the route of injection. After 
subcutaneous injection it may not appear for twenty-four hours ; intra- 


peritoneal injections may require three or four hours for results, 
whereas intravenous injections may be effective in a few minutes. An 
experiment quoted from Besredka illustrates the rapidity and extent 
of the process. Guinea-pigs sensitized with egg-white exhibited fatal 
reactions with a toxic dose of 0.002 c.c. egg-white. An animal of this 
group was given 0.0005 c - c - egg-white intravenously without reaction. 
It did not react to 0.005 c.c., the fatal dose, given two minutes after 
the first injection nor to doses of 0.02 c.c., or 0.2 c.c., given at ten- 
minute intervals. Ten minutes later it was given 2.0 c.c. and, although 
visibly uncomfortable for a time, recovered. Desensitization may also 
be practised by four or five repeated subcutaneous or intraperitoneal 
injections at intervals of about two hours, the subcutaneous route 
requiring a longer time to be effective than the intraperitoneal route. 
We have found relatively large, but still sub-lethal, single doses to be 
most effective by intravenous injections, but less so by intraperitoneal 
and least by subcutaneous injection. Besredka also reports desensitiza- 
tion by introducing the protein into the gastro-intestinal tract but as 
yet this has not received widespread confirmation. Desensitization may 
be effective at any period during the hypersusceptible state. If a second 
dose be given before hypersusceptibility appears, the condition may, 
by subsequent injections, become one of increased resistance 
or immunity. 

Other methods of preventing shock include the use of atropin as 
suggested by Auer and Lewis, of adrenalin, of chloral hydrate, admin- 
istration of ether, alcohol, atoxyl and numerous other drugs. Pelz and 
Jackson found adrenalin most satisfactory in dogs. Karsner and Nutt 
found that atropin sulphate is satisfactory in guinea-pigs provided the 
toxic dose of serum is not too large. The use of adrenalin in guinea- 
pigs is unsatisfactory because of the pulmonary hemorrhage and 
edema which it produces. Drugs which depress the excitability of 
the smooth muscle of the bronchioles, those which depress nerve activity 
generally as the anesthetics, and those which tend to maintain blood 
circulation, are pharmacologically adapted to the prevention of ana- 
phylactic shock. They do not operate as effectively after the toxic dose 
of protein has been given, as they do when given in time to produce 
physiologic effects before the onset of shock. Thomson found that 
exposure to the X-ray inhibits anaphylactic shock. Friedberger and 
Mita have suggested that anaphylactic shock may be inhibited by very 
slow administration of the protein. Lewis has investigated this problem 
experimentally and by the use of the Woodyat pump has found that 
" acute anaphylactic shock can be prevented in sensitized experimental 
animals by giving otherwise fatal doses of diluted antigen intravenously 
at very slow rates." 

Passive Anaphylaxis. As was shown in 1907 by the independent 
investigations of Nicolle, Richet, Otto and Friedemann, the serum of 
a hypersusceptible animal, when injected into a normal animal, will 
render the latter also hypersusceptible. This condition is transferred 
in the serum rather than in corpuscles or tissue cells. Passive ana- 

FIG. 1 8. Tracing from the dog in anaphylactic shock. From 
above downward the tracings are: myocardiograph, blood- 
pressure, base line, membrane manometer, base line, signal, time 
in seconds. The down strokes of the myocardiograph tracing 
represent cardiac contractions. The perpendicular line was 
drawn arbitrarily through the blood-pressure curve at the point 
where the fall began. Corresponding points in the myocardio- 
graph and Hurthle manometer tracings were measured and are 
indicated by the cross where the recording levers were not in 
accurate alignment. (From Eisenbrey and Pearce. A study of the 
action of the heart in anaphylactic shock in the dog. Journal of 
Pharmacology and Experimental Therapeutics, 4, 21. 1912.) 


phylaxis may be demonstrated about four hours after intravenous 
administration of the serum from the hypersusceptible animal, about 
twenty-four hours after intraperitoneal injection and from twenty-four 
to forty-eight hours after subcutaneous administration. It remains 
at its height for about three or four days, gradually disappears in a 
few weeks and never exhibits the permanence of active anaphylaxis. 
Further study by numerous investigators has shown that passive ana- 
phylaxis arises as the result of injection of serum from an animal in 
the hypersusceptible state or from an animal in the " incubation " 
period before sensitization can actually be demonstrated ; it may also 
follow the injection of the serum of an animal in the anti-anaphy lactic 
state and may be produced by the injection of an immune precipitating 
serum. In the last-named instance an animal is immunized to the 
particular protein for which passive anaphylaxis is to be produced. 
Doerr and Moldovan pointed out this fact, and it has been repeatedly 
confirmed. Scott demonstrated that the intensity of the anaphylactic 
shock parallels the titer of the precipitating serum. The young of 
sensitized female guinea-pigs are sensitive, as has long been known. 
The recent work of Reinals confirms this fact, but does not definitely 
settle the question as to whether the sensitization of the young is active 
or passive. 

Specificity of Anaphylaxis. That the process is specific was 
pointed out by the earliest investigators. It is undoubtedly one of the 
most specific of the biological reactions, as is emphasized by its extreme 
delicacy in regard to sensitizing dose. Nevertheless, group reactions 
appear as in the reactions of immunity. For example, a guinea-pig 
sensitive to sheep serum will react somewhat less violently to goat 
serum. Wells and Osborne have shown that cross reactions occur 
between gliadin from wheat and rye, and hordein from barley. The 
reactions, however, are strongest with the homologous protein. Never- 
theless, Wells was able to separate ovovitellin and crystallized egg-white 
by the anaphylaxis reaction and is of the opinion that where group 
reactions occur the reactions are the result of common groups in the 
protein molecules even though the proteins may appear to be chemi- 
cally distinct. If guinea-pigs are sensitized to several proteins simul- 
taneously they will react to any of the proteins employed, but after an 
animal has reacted to one of the proteins, subsequent reactions to the 
others are less severe. Investigations conducted in this laboratory with 
serum proteins indicate that although desensitization is best produced 
by homologous sera it may be effected by biologically-related sera and 
by non-related sera. For such purposes considerably larger doses of the 
heterologous sera are necessary than of the homologous serum. Against 
the assumption that desensitization indicates the specificity of the reac- 
tion is the fact claimed by Banzhaf and Steinhardt that lecithin protects 
against anaphylactic shock. Rosenau and Anderson failed to confirm the 
work of Banzhaf and Steinhardt, but it may well be that a colloidal dis- 
turbance of some sort may prevent the appearance of shock and that 


some similar disturbance may appear as the result of injection of heter- 
ologous sera. 

In view of the great specificity of anaphylaxis it was hoped that 
by this means organ specificity might be demonstrated. Ranzi used 
extracts of liver, kidney, spleen and ovary and found that these gave 
species reactions with serum, but that there was no evidence of organ 
specificity. Pfeiffer pointed out that the organs employed by Ranzi 
contained blood and therefore could not be expected to show more 
than species reactions. He washed the organs apparently free from 
blood and found that animals sensitized to a given organ extract respond 
somewhat more markedly to that extract than to extracts of other 
organs, i.e., there is a relative specificity. This was found to be true 
in somewhat lesser degree by Pearce, Karsner and Eisenbrey. Minet 
and Bruyant desensitized with serum and then attempted to produce 
shock by the organ extracts ; they failed to demonstrate organ specificity. 
Bell has pointed out the fact that the most careful perfusion of organs 
fails to remove the blood completely, and it appears that Minet and 
Bruyant's conclusions must hold for the present. Extracts of sperma- 
tozoa and of ovary fail to exhibit organ specificity, but crystalline lens 
behaves as it does in the reactions of precipitation and cytolysis. 
Numerous investigators have shown that the lenses of different species 
react with each other but that serum fails to interact as either sensi- 
tizer or intoxicating body with the serum of the species from which 
the lens was taken. 

There is no doubt that anaphylaxis produced by bacterial 
emulsions or extracts is specific, but reports vary as to the presence 
of group reactions. Delanoe holds that group reactions appear, 
whereas Kraus and his collaborators maintain the absolute specificity 
of bacterial anaphylaxis. 

Theories of the Reaction of Anaphylaxis. In order to avoid any 
more confusion than is necessary it seems well to review these theories 
in groups rather than in historical sequence. The most important 
difference of opinion is as to whether or not a poisonous substance is 
produced in the reaction. If not it would appear to be necessary to 
suppose that some sort of reaction occurs in the cells of the body or 
in the body fluids, perhaps in the nature of a liberation of energy on 
the part of the cells or in some form of disturbed colloidal or enzymatic 
balance of the fluids. If a toxic substance is formed it may be pro- 
duced in the cells or in the circulating fluids. This may be the result 
of partial destruction of the proteins of the body or of the introduced 
protein, or it may appear as a new body which is formed by substances 
produced by the first injection coming in contact with the antigen upon 
second injection. This summary gives the essentials of the con- 
troversy, and a further elaboration follows. 

Anaphylactic Poisons. Richet formulated the hypothesis that the 
primary injection of protein produces a substance in the body which 
he named toxogenine. Upon second injection the antigen is supposed to 
combine with the toxogenine which has been produced during the period 


of incubation and forms a toxic substance named apotoxine. He com- 
pares the reaction to the combination of amygdaline and emulsine to 
produce hydrocyanic acid. This hypothesis resembles somewhat that 
of Friedberger, which has been investigated intensively by many 
workers. Friedberger prepared a toxic substance, which he named 
anaphylatoxin, by mixing antigen, precipitating serum and complement. 
He obtained a precipitate by mixing sheep serum with a specific immune 
precipitating serum from the rabbit. This precipitate was washed, sus- 
pended in fresh guinea-pig serum for twelve hours, then centrifuged. 
The supernatant fluid was found to be extremely toxic for guinea-pigs. 
The reduction of complement in anaphylaxis has been emphasized by 
Friedberger in the development of his hypothesis concerning ana- 
phylatoxin. Thomson, however, has found that this reduction is not 
constant and that it is in proportion to the quantity of the free antibodies 
in the circulation. It is insignificant when the animal has been sensi- 
tized with a small single dose of antigen, but if the animal has been 
sensitized by repeated doses and the precipitin content of the blood is 
high, the diminution in complement is likely to be marked. The symp- 
toms following injection of anaphylatoxin include the usual clinical 
manifestations, with fall of temperature, retardation of coagulation of 
the blood and leucopenia. The poison resists heat at 56 C. for one-half 
hour, resists desiccation and is precipitated by alcohol. Subsequently 
it was found that bacteria and their antisera could be employed in the 
same fashion as the precipitinogen and precipitin. Doerr and Russ 
found that precipitates are toxic without the addition of complement, 
and in view of this fact and the production of passive anaphylaxis by 
precipitating sera, reached the conclusion that precipitin and the sub- 
stance produced by the primary injection in anaphylaxis are inseparable. 
Kraus and his co-workers have contradicted this parallelism and point 
out that the guinea-pig is a poor producer of precipitin; rabbits may 
produce a powerful anaphylactic substance without producing precipi- 
tins; goats produce precipitin readily but have a serum incapable of 
conferring passive anaphylaxis. Biedl and Kraus pointed out the fact 
that injections of pepton produce symptoms similar to anaphylaxis in 
the dog. Karsner has confirmed this in the guinea-pig. Biedl and 
Kraus found that following injection of pepton into a dog the animal 
subsequently fails to react to anaphylaxis and hence they formulated 
the hypothesis that the poison of anaphylaxis is a pepton-like body. 
Doerr offered the hypothesis that the actual disturbance is in the physi- 
cal character of the blood. He assumes, however, that this disturbance 
is produced by a toxic agent originating in complement. The com- 
plement is supposed to contain the toxic substance held in check by an 
antagonistic substance ; the latter is adsorbed by precipitates or bacteria, 
thus liberating the toxic substance. The further investigation of the 
so-called anaphylatoxin led to the discovery by Keysser and Wasser- 
mann that a similar substance could be produced by the action of com- 
plement on barium sulphate or kaolin. Besredka then found that placing 
fresh serum upon pepton agar produces a toxic fluid which induces 


symptoms identical with those from anaphylatoxin. Bordet found that 
the action of fresh serum upon agar in solution produces a similar 
toxic substance. Novy and De Kruif have published very extensive 
studies upon toxic materials in a measure similar to the anaphylatoxin. 
It is found that the action of serum upon agar intensifies the toxic 
power of the agar. They have shown that agar and other non-protein 
colloids produce anaphylactoid symptoms. 

The poison, if there be such in anaphylaxis, is not dependent on the 
presence of any antibody or other substance within the cells of the sensi- 
tized animal, because it can be produced in vitro; neither is it dependent 
on antigen, inasmuch as barium sulphate and kaolin serve a similar pur- 
pose; nor is it dependent on complement, for, as Doerr has shown, it 
can be produced without the action of fresh serum. Besredka maintains 
that the anaphylatoxin produces no symptoms by sub-dural injection 
and that it kills only upon intravenous injection. Besredka has found 
that pepton does not interfere with true anaphylaxis in the guinea- 
pig, but that it does inhibit the action of anaphylatoxin. Furthermore, 
the state of anti-anaphylaxis which protects an animal against a massive 
dose of the antigenic substance and therefore prevents anaphylactic 
shock has no such protective influence upon anaphylatoxin. These 
arguments as well as those presented in the subsequent section on the 
cellular theories of anaphylaxis serve to show that there is prob- 
ably no poison, which can be produced in -vitro, that leads to the 
development of a condition identical with true anaphylaxis. Certain 
features of this discussion will be referred to under the heading of 
Anaphylactoid Phenomena. 

Cellular Theories. The conflicting views are that either a poison 
is produced within cells, or that some disturbance of cells appears inde- 
pendently of the production of a poisonous substance. Gay and 
Southard, influenced perhaps by the prevailing conceptions of immune 
reactions and impressed by the cellular degenerations seen in their 
animals, emphasized the intracellular character of the reaction. They 
assumed that the injected protein contains a substance, anaphylactin, 
which is eliminated from the body extremely slowly, in contrast to the 
fairly rapid elimination of the other constituents of the protein. " The 
anaphylactin, however, remains and acts as a constant irritant to the 
body cells, so that their avidity for the other assimilable elements 
of the horse serum (or protein), which have accompanied the ana- 
phylactin, becomes enormously increased. At the end of two weeks of 
constant stimulation on the part of the anaphylactin, and of constantly 
increasing avidity on the part of the somatic cells, a condition has 
arrived when the cells, if suddenly presented with a large amount of 
horse serum, are overwhelmed in the exercise of their increased assim- 
ilating functions and functional equilibrium is so disturbed that local 
or general death may occur." This theory was supported by their 
statement that the sensitizing fraction of serum is contained in the 
globulin fraction and that the other elements of serum may serve to 
produce shock. They could not produce a toxic body by mixing the 


serum of sensitized guinea-pigs and horse serum. The fact that 
further investigation, as for example that of Wells and of Kato, has 
failed to demonstrate a manifest difference between sensitizing and 
intoxicating fractions of the protein, is an argument against this 
hypothesis. Friedberger's original conception was that the primary 
injection leads to the development of receptors in the cells but in such 
small amounts as not to be liberated into the blood stream. These 
" sessile " receptors are responsible for an increased affinity of the 
cells for the antigen, the consequent disturbances resulting from the 
rapid anchoring of the protein by the cells. If injections are repeated 
before the anaphylactic state is developed the receptors are formed in 
large amounts and appear in the blood stream as precipitins. This 
hypothesis accords well with the modern conception of immunity and 
anaphylaxis save for the assumption that the sensitizing substance and 
precipitins are identical. This theory was followed by Friedberger's 
anaphylatoxin theory. Somewhat more concrete is the hypothesis of 
Vaughan and Wheeler. After a long period of study of toxic frac- 
tions of bacterial and other proteins by Vaughan and his co-workers, 
the following statement in regard to anaphylaxis was made. " When 
a foreign protein is introduced into the blood or tissues it stimulates 
certain body cells to elaborate the specific ferment which will digest 
that specific protein. When this protein first comes in contact with 
the body cells, the latter are unprepared to digest the former, but this 
function is gradually acquired. The protein contained in the first 
injection is slowly digested, and no ill effects are observable. When 
subsequent injections of the same protein are made, the cells prepared 
by the first injection pour out the specific ferment more promptly, and 
the results are determined by the rapidity with which digestion takes 
place. The poisonous group in the molecule may be set free rapidly, 
and in amounts sufficient to produce symptoms, or to kill the animal." 
Jobling and his co-workers, however, have reached the conclusion that 
the development of proteases in the blood is not dependent upon anti- 
bodies and is not specific. Vaughan replies to this objection that " we 
have only transferred the problem of specificity from the development 
of a specific enzyme to the specific uncovering of a non-specific 
enzyme." Undoubtedly, the bodies studied by Vaughan are extremely 
toxic. As an example, he found that the product of i gram of casein 
is sufficient to kill 800 guinea-pigs. We are not ready to admit that 
toxic substances of this sort produce clinical and pathological changes 
that are identical with anaphylaxis. Weil has given the participation 
of the cells most extensive study. He considered that the cells are of the 
utmost importance in the destruction and elimination of foreign protein 
and that in the course of this process they construct an antibody. The 
union of antigen and antibody within the cells gives rise to the serious 
disturbances which constitute anaphylaxis. His excellent work was 
interrupted by his death in the service of his country, but his hypothesis 
is one which serves equally well in the phenomenon of desensitization 
and in anaphylaxis. In support of the assumption that the primary 


change is in the cells may be considered the work of Schultz, Dale, 
Woods and others with isolated sensitized organs containing smooth 
muscle. These organs, washed free of blood, responded specifically to 
the protein with which the animal was sensitized. Of considerable 
value was the experiment of Pearce and Eisenbrey, who transfused 
dogs so that the blood of a sensitized dog circulated in the body of a 
normal dog and vice versa. Under these circumstances the intoxicating 
dose of the antigenic protein produced symptoms in the sensitized dog 
with normal blood, but no symptoms in the normal dog provided with 
blood from its sensitized fellow. Coca confirmed this with the guinea- 
pig. Although Manwaring and collaborators have found that per- 
fusion of rabbit heart indicates that anaphylactic shock is entirely 
humoral, subsequent work of Manwaring and Kusama with perfusion 
of guinea-pig lungs showed that the cells of the lungs of sensitized 
animals respond by bronchiolar constriction to perfusion with antigenic 
serum. They also found that perfusion of normal lungs with a mixture 
of the blood of a sensitive animal and antigen also produces bronchiolar 
constriction. None of the experiments so far outlined establishes 
definitely the parts the cells play, for, as Bell points out, none of these 
methods has completely removed the native blood from the organs. 
We know that minute amounts of certain protein poisons are highly 
toxic, and it may be that the amount of blood left in a perfused organ 
is sufficient for the production of a humoral poison. Nevertheless, 
studies of passive anaphylaxis tend to confirm the conception of cellu- 
lar participation. Weil has pointed out that simultaneous injection of 
a serum, capable of producing passive anaphylaxis, and its antigen fails 
to produce symptoms. A certain interval of time must elapse before an 
animal becomes passively anaphylactic, an interval in which it is pre- 
sumed the cells either anchor or develop the sensitizing substance. 
Isolated organs fail to respond to the antigen until a certain time has 
elapsed. The time element depends to a certain extent upon the mode 
of injection, but is never less than several hours even with intravenous 
injection. This fact, in association with the experiments in active 
anaphylaxis, in vitro, with perfusion and with isolated organs, all tend 
to support the conception that the participation of the cells is of funda- 
mental importance in the reaction. Weil has studied further the phe- 
nomenon of desensitization and finds that the reaction between the 
cellular antibody and the antigen follows in a general way the Danysz 
phenomenon (see page 50). By the fractional injection of antigen the 
substance in the cells takes up the antigen so that subsequent additions 
of antigen produce little effect. He states that " partially combined 
cellular antibody manifests a marked diminution in its affinity for fresh 
antigen." Thus the conception of cellular participation fits the demon- 
strated facts of passive anaphylaxis. 

Physical Theories. These have been less susceptible to experi- 
mental proof than other theories because of the limitations of technic. 
As has been mentioned, Doerr conceived the idea that adsorption of the 
supposed antagonistic substance of complement by bacteria or precipi- 


tates liberates the toxic substance of complement. This theory omits 
consideration of the cellular participation and needs further elaboration 
to be acceptable. Of more significance is the fact demonstrated by 
Jobling, Petersen and Eggstein that anaphylactic shock " is accom- 
panied by (a) the instantaneous mobilization of a large amount of 
non-specific protease, (b) a decrease of antiferment, (c) an increase 
in non-coagulable nitrogen of the serum, (d) an increase in amino- 
acids, (e) a primary decrease in serum proteoses." They conclude that 
the " intoxication is brought about by the cleavage of serum proteins 
(and proteoses) through the pepton stage by a non-specific protease " 
and that " the specific elements lie in the rapid mobilization of this 
ferment and the colloidal serum changes which bring about the change 
in antiferment titer." From our discussion of the cellular participa- 
tion in anaphylaxis the conception of Jobling cannot be accepted as 
entirely satisfactory, but it has more ground in demonstrated fact than 
any of the other physical theories. Support for Jobling's conception 
is furnished by Bronfenbrenner and others. Bronfenbrenner finds, 
however, that the state of dispersion of the colloids is important in 
maintaining the ferment-antiferment balance and that simply bubbling 
ether through serum decreases the antitryptic activity probably because 
of an increased dispersion of colloidal particles. A similar decrease 
of antitryptic activity of the blood follows a mixture of antibodies and 
antigen. This theory may be applied to desensitization by assuming 
that the small intoxicating dose inhibits antiferment, that the proteases 
then operate and that the split products act as antitrypsin, thus prevent- 
ing the toxic effects of subsequent injections. Danysz hypothesizes that 
anaphylaxis is an intracellular or intravascular disturbance of digestion 
or a combination of the two. The disturbance of digestion consists in an 
inability of the organism rapidly to transform the colloid antigen into 
crystalloids. The symptoms are produced by a sudden alteration of 
equilibrium between the sol. and gel. state of the colloids which enter 
into the composition of the cells and of the blood. His conclusion that 
acute anaphylaxis is due to intravascular changes in the animal is in 
contradiction to what we believe to be well demonstrated facts. Krits- 
chewsky found that the sap of a certain plant, cotyledon scheideckeri, 
precipitates blood proteins, agglutinates and hemolyzes erythrocytes. 
Symptoms in animals following injections into the circulation or sub- 
cutaneously resemble anaphylaxis and are due, Kritschewsky believes, to 
a change in degree of disperseness of the plasma colloids, and he 
therefore assumes that anaphylaxis is of the same nature. We do not 
concede that Kritschewsky worked with true anaphylactic shock, as 
the pathological findings in his animals lack the uniformity of those 
seen in true anaphylaxis. Similarly we object to the experiments of 
Doerr and Moldovan who produced toxic symptoms by the injection 
of water colloidal solutions of silicic acid, also of nucleinic acid and 
of dialyzed iron hydroxid. Kopaczewski found that the injection of 
serum rendered toxic by addition of bacterial suspension or colloidal 
gels., when injected into animals reduces the surface tension of their 


blood three or four dynes, from which reduction the animal gradually 
recovers. Upon investigation of the electrical potential of sera it was 
found that a current of eight volts shows a precipitate at both electrodes 
in the case of normal serum, but that with a so-called anaphylactic serum 
the precipitate collects almost entirely in the negative pole. Although 
Besredka's former idea that the injected serum contains a separate 
sensibilisinogen which leads to the formation of sensibilisin in the cells, 
and an antisensibilisin which combines with sensibilisin upon the second 
injection of the serum is not in accord with prevailing ideas, yet he was 
one of the first to propose a physical theory. Thus he stated in a gen- 
eral way the majority of the facts seem to indicate that the phenom- 
ena of anaphylaxis and anti-anaphylaxis are reduced to the action of 
precipitation and adsorption which upset the mutual relations of the 
colloids. Besredka no longer insists upon the separation of the two 
elements of protein, but is of the opinion that the important site of 
reaction is in the nerve cells. He believes that the second injection 
of the protein meets with the preformed sensibilisin in the cells and 
produces there either a liberation or absorption of energy, thermal or 
otherwise, and that this reaction leads to the phenomena of anaphylactic 
shock. He compares the reaction to the mixing of water and sulphuric 
acid. If the water is added suddenly to the acid there is an explosive 
liberation of the heat of hydration. If the water is added slowly, the 
heat is generated more gradually and no serious manifestations take 
place. So with anaphylaxis, if the injection is in a single large dose, 
anaphylactic shock is produced, but if several small doses are given, 
there is a series of very slight shocks leading to no serious disturbance 
and so desensitizing the body that serious results cannot follow a 
subsequent large injection. Besredka argues that the inhibitory effect 
of anesthetics supports his contention that the nerve cells are of great 
importance in production of anaphylactic shock, but the work of numer- 
ous investigators shows that the broncho-constriction and fall in blood- 
pressure occur in spite of anesthesia, and that the reaction may be fatal 
if the intoxicating dose be sufficiently large. Bronfenbrenner points 
out that anesthetics increase the antitryptic power of the blood 100 
per cent, or more, thus inhibiting the liberation of proteases and the 
consequent production of toxic split products. As a further objection 
to Besredka's conception is the fact that the experiments with isolated 
organs and perfusion demonstrate that smooth muscle reacts and that 
the phenomenon is by no means confined to the nerve cells. When 
calorimetric and metabolism experiments can be performed with nerve 
tissues, definite information can be obtained in regard to energy changes 
in these tissues in anaphylaxis. 

Anaphylactoid Phenomena. In the discussion of the theories of 
anaphylaxis references have been made to anaphylatoxin and certain 
similar substances. As has been pointed out, these substances may be 
protein in character, may represent certain decomposition products of 
protein, or may be non-protein colloids. It is even maintained that 
arsphenamine is to be included in this category of colloids. The in- 


vestigation of these substances has had an important bearing on the 
development of theories of anaphylaxis, because if these can be com- 
pared to the supposed toxic substance of anaphylaxis it would seem 
reasonable to suppose that anaphylaxis has as its basis a colloidal dis- 
turbance. Many of those who have worked with these substances 
have not been strict in their use of the term anaphylaxis and have 
depended in large part on the clinical manifestations following the injec- 
tions of these agents. From time to time certain investigators have 
indicated that more intimate study would prove that anaphylaxis and 
the phenomena following the injection of these colloids are not identi- 
cal. Manwaring and Crowe, for example, found that occasionally there 
appears in anaphylaxis occlusion of pulmonary blood-vessels by thrombi 
and used the term pseudo-anaphylaxis. The problem has recently been 
investigated extensively by Hanzlik and Karsner. The experiments 
in this series of studies were controlled by gross and microscopic studies 
of the viscera of the animals after death. More than thirty colloidal 
agents were studied by a variety of methods, including intravenous 
injection, studies of perfused organs, protection by atropin and epi- 
nephrin, as well as test-tube studies of the action of the agents upon 
blood-corpuscles. Many of the agents studied produce serious dis- 
turbances of circulation and others produce equally serious disturb- 
ances of respiration. In the case of none of these colloids was it 
possible to demonstrate that the clinical and morbid anatomical phe- 
nomena, taken collectively, are identical with those of anaphylaxis. 
The symptoms provoked can all be explained on grounds other than 
the assumption that we are dealing with anaphylaxis. Even in the case 
of agar, where bronchial constriction and pulmonary distention are well 
marked, the common occurrence of thrombi both in the living animal 
and in perfused lungs definitely excludes an identity with anaphylaxis. 
These phenomena may, therefore, be considered as of colloidal nature 
and may well be referred to as " colloid shock." Pepton produces symp- 
toms and signs more nearly like those of true anaphylaxis than the other 
substances studied, but the fact that pepton more frequently produces 
thrombosis, hemorrhage and edema of the lungs than is the case in true 
anaphylaxis, would place pepton poisoning in the group of ana- 
phylactoid rather than anaphylactic phenomena. Similarly the injec- 
tion of primarily toxic sera such as ox serum and eel serum into the 
guinea-pig produces certain circulatory disturbance with hemorrhage 
and edema. It seems probable that the toxicity of some of the sub- 
stances of protein nature or the decomposition products of protein may 
depend for their activity upon the presence of histamine. The poison- 
ous character of histamine depends in no way upon previous sensitiza- 
tion, is primarily toxic and therefore may be included as anaphylactoid 
in its action. 

Summary. With a strict adherence to the conception that ana- 
phylaxis constitutes that state of hypersusceptibilityto a given substance, 
which has been induced by a previous injection of the same substance 
we may conclude that the mode of the second injection determines the 


particular manifestations observed. The sensitizing fraction of the 
protein, if there be any such fraction, has not been isolated nor has 
the intoxicating substance. If the second dose be given in mass, ana- 
phylactic shock results. If, on the other hand, divided small doses are 
given the state of the organism is so changed that severe anaphylactic 
shock does not appear. In agreement with Besredka, we believe that 
desensitization produces a series of minor shocks but believe that the 
explanation lies rather in the work of Weil than in the hypothesis of 
Besredka. In other words, there is a partial saturation of the sensi- 
tizing substance within the cells, so that any subsequent union cannot 
produce the intensity of reaction that would have been produced by a 
massive injection. The time that must elapse for the production of 
passive anaphylaxis, as well as the other experiments offered in evi- 
dence, support the conception that some change must occur in the cells 
in order to produce sensitization. The nature of the combination 
between the specific protein and the substance within the cells or the 
influence of the protein upon the cells is not definitely known, but the 
data offered in review appear to rule out the probability that definite 
toxic bodies are formed. Similarly the nature of the primary changes 
in the cells upon second injection cannot be identified; as to whether 
there is a liberation of energy of some sort or a disturbance of colloidal 
relations must still be the subject of investigation. The specificity of 
the reaction is similar to that of other biological reactions and is subject 
to similar limitations of the group phenomenon. Nevertheless, we find 
in anaphylaxis a most specific phenomenon, which is approached 
in delicacy only by the reactions of precipitation and of com- 
plement fixation. 

The Relation of Anaphylaxis to Immunity. If desensitization of 
an anaphylactic animal is carried on for only a short time the period of 
desensitization is relatively brief, but, on the other hand, if the vac- 
cination be continued the animal may be rendered resistant. This indi- 
cates a close relationship between the two phenomena. We do not 
propose to discuss this at length because of the intricacy of the subject. 
Weil pointed out in his earlier experiments by saturation of the animal 
with proteins that although the animal may become immune in so far 
as his body fluids are concerned he may remain hypersensitized in so 
far as his cells are concerned. Manwaring and Kusama found that 
the lungs of guinea-pigs immunized to a certain protein, when washed 
free of blood, were still sensitive to perfusion with the protein in 
question. We, therefore, revert to the conception of Weil that im- 
munity is in large part exhibited in protective power of the blood and 
body fluids. In the state of anaphylaxis this immunity has not been 
established in the fluids and therefore the cells can be directly operated 
upon by the antigen. If, on the other hand, the animal is immune his 
blood and fluids combine with the antigen so as to protect the cells. 
The direct bearing of this upon diseases in man is a matter of specula- 
tion. It seems possible, however, that during the period of incubation 
of an infectious disease the animal, as suggested by Danysz, likewise 


passes through the period of sensitization to the infecting organism. 
When, therefore, the infecting organism or its products are present in 
sufficient amounts the manifestations of disease appear in the form of 
what may be termed an acute or sub-acute anaphylaxis. As time goes 
on this process is transformed into an immunity and the disease under- 
goes cure. In this latter state it may be assumed that the body fluids 
have developed a sufficient amount of protective substance so that the 
cells are no longer susceptible to attack. This would satisfactorily 
explain the self-limitation of .infectious disease. By assuming that 
injury of the cells may have become so serious as completely to 
interfere with life processes, death may ensue, or if the disturb- 
ance is not so severe the condition may exhibit the chronic com- 
plications which so frequently follow acute infection. 











Introduction. The manifestations of hypersusceptibility in man 
can be classified into two groups, those in which a definite previous sensi- 
tization has been effected and those in which no such sensitization is 
known or can be conclusively proven. In the former group are 
included a relatively few cases of anaphylactic shock and the widely- 
observed phenomenon called serum disease. In the latter group are 
those individuals who are abnormally sensitive to a wide variety of sub- 
stances. These may gain access to the body from the air, through the 
respiratory tract, skin or conjunctiva or through ingestion of foods 
which contain the specific substance. In addition to air contacts, direct 
contacts with plants and animals, which may or may not serve to produce 
dusts, may also lead to dermal manifestations of hypersenstiveness. 

Serum Disease. The Delayed Reaction. The serum treatment of 
various diseases has given ample opportunity for the study of the 
symptom complex called by von Pirquet and Schick serum disease. 
This follows with extreme frequency upon subcutaneous, intravenous or 
intrathecal injections of animal sera employed for therapeutic pur- 
poses and may be delayed or accelerated. The symptoms may develop 
after a primary or series of primary injections and constitute the delayed 
reaction. These symptoms appear from six to twelve days after the 


injection, and in our experience have been most frequent after ten to 
eleven days. The most noticeable and most common symptom is a skin 
eruption which is usually urticarial but may be a patchy or diffuse 
erythema, a scarlatiniform or a multiform eruption. Edema may 
appear in the lips, eyelids, face or other parts of the body and rarely 
may effect the larynx. According to Longcope, " in one instance a 
transient hemiplegia was supposed to be caused by local edema of the 
meninges." We have seen one case in which a broncho-pneumonia, 
following a prophylactic injection of serum appeared to be the sequence 
of an edema of the bronchi. There is often lymph-node enlargement, 
which may precede the eruption and may be accompanied by enlarge- 
ment of the spleen. There is likely to be a moderate fever, headache, 
malaise and occasionally nausea and vomiting. Multiple joint pains, 
increased by motion, but without tenderness, redness or swelling, are 
common in severe cases. Albuminuria appears in 5 to 9 per cent, 
of the cases, and Longcope has found that there is likely to be salt 
and water retention with little or no disturbance of nitrogenous elim- 
ination. There may be a primary leucocytosis, followed by a leuco- 
penia, which latter shows an absolute increase of lymphocytes. The 
condition usually lasts twenty-four, forty-eight or seventy-two hours 
and occasionally is prolonged to twenty days or more. Relapses may 
occur, more particularly after the use of large amounts of serum. 

Several factors enter into the occurrence, severity and duration of 
the disease, the larger doses giving more frequent occurrence, greater 
severity and longer duration. There are certainly individual differences 
in the resistance of patients and probably individual differences in 
specimens of serum. Sera from different species exhibit differences 
in toxicity for man, that of the ox, according to Kraus, being less likely 
to produce serum disease than that of the horse. The globulin pre- 
cipitation or so-called concentration of horse serum in the preparation 
of antitoxins reduces the toxic manifestations in man. 

The Accelerated Reaction. Frequently repeated injections of serum 
at properly spaced intervals may lead to a state of resistance or im- 
munity, but this is practically never permanent. Following a primary 
injection or series of injections, there usually develops a state of hyper- 
susceptibility. This condition does not precede the appearance of the 
delayed reaction and does not precede the tenth day after injection, 
even if the delayed reaction fails to appear. Repeated doses of serum at 
short intervals delay the appearance of hypersusceptibility. The height 
of sensitiveness is reached in from two to three months, after which it 
slowly subsides but probably never entirely disappears. We have 
observed accelerated reactions nine and fourteen years after primary 
injection. The hypersusceptibility exhibits itself only on injection of 
the protein and is specific for the species from which it originated. 
Following the second injection of the protein or serum there is occa- 
sionally no acceleration of reaction, but if accelerated it may be mod- 
erately or markedly so, the last producing the so-called immediate 
reactions. These immediate reactions may be local, appear about the site 


of injection in from a few minutes to an hour or two and show edema, 
erythema or urticaria. There may also be a general immediate reaction 
which appears in from twelve to twenty-four hours and in addition to 
the usual symptoms and signs of serum disease may be accompanied 
by severe asthmatic form of dyspnea, cardio-vascular disturbances with 
cyanosis, collapse, chills, nausea and vomiting and renal disturbances 
including complete suppression for several hours. If the second injection 
is given when hypersusceptibility is not marked, as for example after 
a small primary dose, or several years after a primary dose, the accel- 
erated reaction is not likely to be immediate but appears in from two 
or three to five or six days. Under these circumstances the reaction 
may appear as an ordinary case of serum disease or may be more severe. 

Anaphylactic Shock in Man. There is little doubt that the accel- 
erated reactions of serum disease bear in some way a relation to ana- 
phylactic shock. During the period of .hypersusceptibility in man the 
subcutaneous administration of serum rarely if ever produces death, 
in spite of the fact that the clinical symptoms may be extremely severe. 
On the other hand, intravenous injections have been reported to produce 
death following symptoms closely resembling those of anaphylactic 
shock in animals. Reports of accidents of this sort led to the funda- 
mental investigations of Rosenau and Anderson, which have been 
described. Injections of serum into the spinal canal have been followed 
by fatalities, but an analysis by Auer of the reported cases leads him 
to believe that for the most part these deaths were due to other causes 
than anaphylaxis. Miller and Root, in analysis of death following 
subcutaneous administration of horse serum, find that death in some 
instances was probably caused by status thymo-lymphaticus and that in 
other cases the cause of death had not been demonstrated to be ana- 
phylactic. The clinical and pathological picture of fatalities has in most 
instances not been clearly described. Nevertheless, Boughton has 
recently reported a case in which a man, the subject of bronchial 
asthma when near horses, died upon being given intravenously one 
minim of normal horse serum. Autopsy showed enormous distention 
of the lungs with congestion of other viscera and numerous small hemor- 
rhages. This apparently is an instance of true anaphylactic shock in 
man, and it cannot be doubted that such accidents occur. Caution 
must be exercised, however, in attributing death to anaphylaxis because 
of the numerous other conditions which may lead to sudden death, 
particularly in the course of acute infectious diseases. 

Natural Hypersusceptibility. The recent scientific investigations 
of hay fever and its various modifications, as well as asthma, eczema, 
other diseases of the skin, angio-neurotic edema and certain gastro- 
intestinal disturbances, have shown that a considerable number of these 
cases are hypersusceptible to proteins of various origins. The skin 
reactions, to be described subsequently, and the effect of specific treat- 
ment both demonstrate the etiological influence of the special proteins. 
The evidence presented from large clinics devoted to the study of these 
conditions leaves no doubt concerning the fact that many of these cases 


are instances of hypersusceptibility. The sensitive state appears to be 
inherent in the cells of certain individuals, and although not directly 
inherited, Cooke and Van der Veer have found that the tendency to 
spontaneous sensitization appears to be heritable, that it follows the 
law of Mendel and appears as a dominant character. Nevertheless, 
there is a possibility that sensitization may be acquired in some manner. 
Cooke, Flood and Coca maintain that artificial sensitization cannot be 
produced by pollens. Heyl, however, has obtained from the pollen of 
ragweed an albumin, a proteose and a globulin and found that mixtures 
of the albumin and proteose possess definite sensitizing properties upon 
animal inoculation. Individuals who have been given horse serum 
therapeutically become somewhat sensitive to subsequent injections of 
horse serum, but only in rare instances is the sensitiveness shown as a 
coryza or asthma when near horses. The chance of sensitization by in- 
jection of other proteins is not great. The possibility of sensitization 
by virtue of the material gaining access to the body through the respira- 
tory or intestinal surfaces is apparently remote. There is little satis- 
factory evidence that protein materials in the form of dust gain access 
to the circulation through the respiratory membrane. Ulrich, however, 
reports the experimental sensitization of guinea-pigs by nasal insuffla- 
tion of pollens and of horse serum, but reports that rabbits cannot be 
so sensitized. It is impossible, under these circumstances, to exclude 
the possibility that the material is ultimately swallowed, and sensitiza- 
tion effected through the intestinal tract. The ingestion of proteins as 
foods ordinarily leads to such changes in the protein in the process of 
digestion that the absorption of the products cannot produce sensitiza- 
tion. On the other hand, it is known that if given in large amounts and 
given under certain circumstances native protein may gain access to 
the blood stream through the intestinal tract. Rosenau and Anderson 
maintained that sensitization could be effected by feeding horse serum 
to guinea-pigs, but the failure of Besredka, as well as of other investi- 
gators, to confirm this leaves the matter in some doubt. As against the 
acquisition of hypersusceptibility in hay fever, Dunbar and also Cooke, 
Flood and Coca have found that patients may be sensitive to the pollens 
of plants indigenous to foreign countries and with which the patients 
have never come in contact. 

Hay fever, rose fever and similar disturbances are due to the pol- 
lens of certain plants and the flowering period of these plants deter- 
mines the seasonal prevalence of the disease. The pollens responsible are 
those which are disseminated by winds ; those plants which are pollin- 
ated by insects do not produce hay fever. Scheppegrill points out 
also that the direct effects of pollens are of importance as they may 
be locally irritant to both normal and hypersusceptible individuals, 
either because of the mechanical effect of spiculated pollens or because 
of the discharge from the pollen of irritant juices. Local reactions may 
be increased by anatomical malformations in the nose and pharynx, such 
as deviation of the septum, polyps, adenoids, and the condition may 
entirely subside following correction of these abnormalities. Strouse 


and Frank claim that the attacks may be intensified and prolonged 
because of a concurrent acute or sub-acute bacterial infection, which 
perhaps permits greater absorption of the pollen protein. The condition 
may be so severe as to be called asthma, and in addition to respiratory 
phenomena may show erythematous and urticarial eruptions. Similar 
conditions are met with in certain individuals sensitive to the effluvia of 
horses, rabbits and other animals. It is well known that the ingestion 
of certain foods, such as egg albumin, shell fish, strawberries, may give 
rise to serious intestinal disturbances and that these may occasionally be 
associated with skin eruptions or respiratory disturbance. In sensitive 
individuals contact of the skin with plants or animals, to the protein of 
which the individual may be sensitive, leads not uncommonly to cutane- 
ous eruptions. These, however, are not likely to be very severe or of 
long duration. The inflammation of the skin in ivy or sumac poisoning 
is not to be included in this group, because the irritant agent is prob- 
ably not of protein nature, but rather an" acid-resin. Eczema and per- 
haps certain other skin diseases may also be due to hypersusceptibility, 
and it is found that this is exhibited rather toward food products than 
toward other forms of protein. Furthermore, certain of these cases 
of asthma, eczema, etc., may be due to bacterial proteins as well as 
those of higher plants and of animals. 

The hypersusceptibility of the sort discussed in this section differs 
from induced hypersusceptibility in two important respects. In the 
first place, the degree of sensitiveness is extreme. This may be illus- 
trated by the case reported by Boughton, quoted above, in which one 
minim of horse serum produced death. It is further illustrated by the 
fact that hay fever, asthma and other similar conditions are induced 
by what must necessarily be an extremely small amount of protein 
in the atmosphere. In the second place, the sensitization is not limited 
strictly to a single protein. Longcope classifies these individuals roughly 
as those " who react to the sera of animals ; those who react to eggs, 
or the sera of fowls ; those who react to the extracts of shell fish and 
those who react to the protein of plants." Within each group the 
individual may be sensitive to the protein of several species. As has 
been pointed out by Walker, those who react to bacteria frequently 
react to several varieties of organisms. Furthermore, individuals may 
occasionally show reactions to two or three of the large groups indicated 
by Longcope. Of further interest in regard to specificity is the fact 
that apparently within a given species, proteins of somewhat different 
origin may not produce identical reactions. For example, skin reac- 
tions may demonstrate sensitiveness to horse dandruff and not to horse 
serum. Desensitization may be produced by careful and prolonged 
vaccination, but as in experimental animals the desensitized state does 
not persist for a very extended period, it may be necessary to repeat 
the vaccinations every six months, every year, or at such other periods 
as the individual case requires. The possibility of passive sensitization 
in natural hypersusceptibility is illustrated by a case reported by 
Ramirez. A man who had never shown any hypersensitiveness to proteins 


was transfused with the blood of a donor who was a victim of horse 
asthma. The recipient, two weeks later, while driving in a carriage, 
was seized with a typical asthmatic attack and subsequently showed a 
positive skin reaction to horse dandruff. This apparently is a case of 
passive transfer of a natural hyper susceptibility. No data have been 
collected to show whether such a variety of passive sensitization is per- 
manent in man or exhibits the same evanescent character as occurs in 
animals. Passive sensitization of animals has been produced by Koess- 
ler, but Cooke, Flood and Coca, as well as Ulrich, have been unable 
to confirm this. Our own experience with one case of human hyper- 
susceptibility to rabbit serum failed to demonstrate passive transfer 
into guinea-pigs. 

Tests for Hypersusceptibility. The manifestations of hyper- 
susceptibility may be general or local, depending on the mode of in- 
oculation and the amount of material employed. If the dose can be 
carefully regulated, the hypersusceptible state may be demonstrated by 
inducing a general reaction, as in the tuberculin reaction. Owing to the 
fact that individuals may be extremely sensitive to certain proteins, as 
in the case reported by Boughton (see page 230), the use of the general 
reactions for diagnostic purposes is limited to those in which severe 
general reactions are not likely to appear. The local reactions give 
equally satisfactory information in man and are devoid of serious 
results. These local reactions are based fundamentally upon the studies 
of Arthus, published in 1903. He found that if animals are given 
several subcutaneous injections of normal horse serum at three- or 
four-day intervals, the first three injections are absorbed readily, but 
the fourth is followed by a local inflammatory reaction and subsequent 
injections are likely to be followed by more severe inflammation, necrosis 
and gangrene. Animals rendered sensitive by these first two or three 
injections could be killed by intravenous or intraperitoneal injections. 
The Arthus phenomenon was early employed as a means of detecting 
hypersusceptibility resulting from bacterial invasion, but it has now 
found widespread employment in the detection not only of the presence 
of changes incident to infectious disease but also for the determination 
of sensitiveness to a large number of proteins of animal and vegetable 
origin. Although hypersusceptibility may exhibit itself in respiratory 
phenomena as in hay fever, horse asthma, etc., or in gastro- intestinal 
disturbance, as in sensitiveness to egg-white, definite local reactions 
may be evoked by the introduction of the proteins into or under the 
skin and these local reactions may be accompanied by general symp- 
toms, such as fever, headache, malaise and transitory leucopenia fol- 
lowed by slight leucocytosis with an associated esinophilia. 

Toxins in Hay Fever. The studies of Dunbar assumed that the irri- 
tant agent in pollens is a toxin. He based this conclusion on the fact that 
he could prepare a so-called antitoxic serum " pollantin " by immunizing 
animals and subsequently claimed that he could demonstrate antibodies 
by precipitin and complement-fixation tests. Clowes found positive 
precipitation and complement fixation in some but not all cases before 


the beginning of the hay-fever season, which disappeared for a few 
weeks after specific desensitization. On the other hand, numerous 
other investigators have failed to demonstrate such reactions, and this 
phase of the question must be considered unsettled. Dunbar claimed 
that treatment with the antiserum " pollantin " produced specific effects, 
but Weichardt maintains that equally good results are obtained with 
the serum of normal animals taken in the summer season. Cooke, 
Flood and Coca were unable to demonstrate immune reactions in the 
sera of rabbits inoculated repeatedly with the pollens of ragweed and 
of redtop. Other objections to the toxin conception include the fact 
that the majority of normal individuals are, practically speaking, abso- 
lutely resistant to the pollens and fail to react to doses 1000 times the 
dose which produces reactions in susceptible cases. This is not in 
accord with the finding in regard to any other of the known toxins. 
Apparently normal individuals may resist diphtheria toxin, but Cooke 
and Van der Veer have pointed out that' such resistance depends upon 
the presence of demonstrable antitoxin, which is not true in resistance 
to pollens. By mixing the " pollantin " and pollens and then testing 
by an ophthalmic reaction in sensitive individuals Dunbar's assistant, 
Prausnitz, plotted a curve of neutralization, but Wolff-Eisner found 
that this curve does not follow the law of multiple proportions and is 
therefore not similar to other toxin-antitoxin combinations. There 
seems, therefore, little ground for assuming that the pollens contain 
a special toxin and the subsequent work with hay fever and similar 
conditions indicates that they represent a condition of hypersuscepti- 
bility to proteins or to protein decomposition products. 

Technic of Cutaneous Tests. If the antigenic proteins are already in 
solution, as is the case with blood serum, no especial treatment is required 
other than suitable dilution under strictly aseptic precautions. If the protein 
is in solid form, as in the case of vegetable proteins and other cellular forms, 
extracts are required. The studies of Walker and of Wodehouse on the 
preparation of materials for the tests have been of the utmost importance. 
These are independent of the preparation of the various tuberculins, which 
will be discussed subsequently. They found that an excellent dried prepara- 
tion of serum could be obtained by precipitating with several volumes of 
acetone, washing the precipitate centrifugally twice with alcohol and with 
ether, and drying to a powder. The powder may be applied to an incision in 
the skin and dissolved with N/io NaOH solution. Bacteria are cultivated on 
solid media, washed centrifugally in salt solution, then twice in absolute alcohol 
with 0.5 per cent, phenol added, twice in ether and then dried to a powder, which 
may be used as is the serum powder. Cereals, nuts and other seeds, roots 
and tubers, fruits, leaves and stems are extracted in water, precipitated with 
95 per cent, alcohol, washed with 95 per cent, alcohol, absolute alcohol, ether 
and desiccated over hydrochloric acid. Hair and dandruff of animals may 
be employed as a dissolved extract in 14 per cent, alcohol, but for more 
accurate studies, dried preparations of acid metaprotein, alkali metaprotein 
and pepton extracted from the material are employed. 

The methods of inoculation include introduction of the protein into 
abraded surfaces and intracutaneous injection through a fine needle. In 
special instances, as, for example, in the use of tuberculin, the material may 
be incorporated in an ointment and carefully rubbed into the skin; this is 
the so-called percutaneous test. Somewhat similar to the cutaneous tests is 
the ophthalmo-reaction, more particularly applied in tuberculin tests, where 
the material is instilled into the epnjunctival sac. Subcutaneous injection of 
material is also resorted to, again with tuberculin rather than with other 


substances, but the determination of results is by means of the general 
rather than the local reaction. As with other reactions, controls are a neces- 
sary part of these tests. The cutaneous test, by which is meant introduction 
of material into an abrasion, is performed as in smallpox vaccination. Any 
part of the body may be selected, but we have found the arm most con- 
venient. Walker advises making small incisions in the skin, deep enough to 
permit absorption, but not deep enough to cause bleeding. A small dental 
burr may be used, as in the Schick test. The material is placed on the 
abrasion or incision and allowed to remain one-half hour. If a powder, a 
solvent should be added after the powder is placed on the skin. If not com- 
pletely soluble in water, a weak solution of sodium hydroxide, either o.i per 
cent., or N/io may be employed, as it does not affect the reaction. Walker's 
studies show that for detecting hypersensitiveness in cases of asthma, hay 
fever, etc., the cutaneous test is more delicate and yields fewer false positive 
reactions than the intracutaneous test. 

The delicacy of these tests is probably greater than that of any 
other biological reaction. As has been stated, patients sensitive to 
extracts of hair of an animal may not be sensitive to the serum proteins 
and vice versa. Very small amounts of antigen suffice to produce reac- 
tions; alkali metaprotein and pepton from hair and dandruff give 
reactions commonly in dilutions of I 10,000 and Wodehouse reports 
one case in which reactions were obtained with dilutions of 1-1,000,000. 
Clowes reports reaction by means of the ophthalmic test to 0.000,000,05 
gram pollen. The fact that positive reactions are found with cutaneous 
tests in individuals whose serum fails to exhibit antibodies by pre- 
cipitation, agglutination and complement-fixation tests, is a further 
indication of the delicacy of the reaction. The accuracy of the reac- 
tions is supported by the beneficial results of specific vaccination or 
desensitization. The treatment is usually by means of subcutaneous 
injections of the protein to which the patient is sensitive. In cases of 
sensitiveness to food products, as well as in other cases, patients may 
be vaccinated by giving the protein by mouth. In either method the 
amounts are extremely small, and in most instances the course of treat- 
ment must be repeated at intervals which may vary from a few months 
to a year or more. The intracutaneous test appears to be the most 
delicate in producing local reactions, but unfortunately is more likely 
to produce confusing traumatic and non-specific reactions to be de- 
scribed subsequently. Details of treatment are given in numerous 
articles, such as those of Blackfan, Talbot, Goodale, Berger and others 
in the recent literature. 

The Reaction. This depends to a certain degree upon the particu- 
lar cutaneous test employed and the sensitiveness of the patient, but in 
a general way the description applies to all the methods. An urticarial 
wheal may appear within a very few minutes and may persist for from 
several minutes to several hours, elevated, firm, pale and itching. Either 
with or without this preliminary reaction, the passage of a few hours, 
six, twelve, twenty-four or more, reveals a local area of inflammation 
about 10 m.m. in diameter, elevated, papular, red, firm and tender. In 
severe reactions the area may reach a diameter of several centimetres, 
may be surrounded by an areola of subcutaneous edema, may show 
fine punctate hemorrhages and may ultimately show vesicles and 


crusts. In unusually sensitive individuals the local reaction may be 
accompanied by systemic manifestations. Less severe but sometimes 
confusing reactions may appear in the form of pseudo-reactions 
which are non-specific in nature and probably due to the 
action of body proteases upon introduced proteins. The reaction 
to the traumatism from the introduction of the protein may at times 
be, somewhat confusing but in most instances is slight. Certain drugs, 
such as iodides and bromides, appear to increase the intensity of reac- 
tions whether they be specific or non-specific. Iodides are known to 
reduce the anti ferment titer of the blood, and it is possible that the 
use of these drugs therefore liberates protease and in this way acceler- 
ates the non-specific local reaction. The increase of the specific local 
reactions is probably due to the increase of the non-specific interaction 
of protease and the introduced protein. 

Theories of Cutaneous Reactions. The appearance of local reac- 
tions in hypersusceptibility may be explained according to any of the 
theories offered for anaphylactic shock. If the mechanism of ana- 
phylaxis involves the formation of poisons these may be concentrated 
in situ because of the irritation produced by introducing the antigen. 
The irritation leads to a slight local inflammation with its incident vaso- 
dilatation and edema. Thus there is a local concentration of antibody, 
which in reaction with the introduced antigen produces a hypothetical 
poisonous substance. If the sensitizing substance is within cells, the 
local contact of antigen in the tissues of the skin explains the local 
reaction. Similarly the physical theories are adaptable. Stokes, for 
example, has found that agar will produce a local non-specific reaction. 
This is probably the result in part of a local loss of balance between 
ferment and antiferment due to adsorption of the latter by the agar. 
Similarly any of the physical theories might apply, but the acceptance of 
the importance of the cells in the reaction, whether physical or other- 
wise, offers an excellent reason for the early appearance and severity 
of the local reaction without general manifestations. Cooke, Flood and 
Coca state that antibodies are not demonstrable in the blood of naturally 
sensitive persons and therefore emphasize the essential importance of 
the cells. .While agreeing that the cells play a most important part, 
the experiments of Koessler and the case reported by Ramirez suggest 
that natural sensitization is of essentially the same nature as anaphylaxis, 
with marked differences only in the degree of cellular and humoral 
participation. Therapeutic desensitization of man lasts for a relatively 
short period of time and differs only in duration from desensitization 
in experimental animals. In both cases the phenomenon is specific 
for the antigen employed. 

Gay and Force, Gay and Claypole, and Gay and Minaker, in their 
work with cutaneous reactions in typhoid fever and in the carrier state 
in meningococcus infections, have expressed the opinion that positive 
reactions are an indication of resistance on the part of the body against 
infection by the organisms concerned. Nichols studied the typhoidin 
test (see page 242) in individuals who had survived typhoid fever and 


found that only 75 per cent, of these reacted positively, whereas experi- 
ence has shown that at least 90 per cent, of such individuals are 
immune to reinfection. He also pointed out that the immune state 
following an attack is of much greater duration than is indicated by the 
typhoidin test. Furthermore, those who have survived typhoid fever or 
have been vaccinated with bacillus typhosus react positively to para- 
typhoidin, but it is known that these individuals are not immune to 
paratyphoid fever. Kolmer and his associates have found no con- 
stant parallelism between the presence of positive cutaneous tests 
and those circulating antibodies, whose presence is indicative of im- 
munity. " The positive anaphylactic skin reaction is, therefore, evidence 
of infection or sensitization to a particular protein without bearing any 
direct relation to resistance to infection or reinfection." 

Drug Idiosyncrasies. It is well known in connection with certain 
drugs, such as morphin, that prolonged use makes it necessary to in- 
crease the dose in order to obtain physiological effects. This increase in 
resistance to morphin is specific, but in the case of chronic alcoholism 
the individual's resistance to somewhat related substances, such as 
chloroform and ether, is also increased. Experiment fails to show that 
this resistance is a state of immunity, and no immune reactions 
in the ordinary sense of the term have been demonstrated. The use 
of certain drugs, such as iodof orm, iodides, bromides, coal-tar products 
and quinine, sometimes gives evidence on the part of the patient of 
a special susceptibility or idosyncrasy in the form of cutaneous erup- 
tions and more or less severe general symptoms. Both Bruck and 
Klausner expressed the view that this is an evidence of hypersuscepti- 
bility similar to or identical with anaphylaxis. Inasmuch as anaphylaxis 
is a phenomenon concerning proteins, Bruck offered the hypothesis 
that the drugs enter into combination with the body proteins, so that 
a new drug-protein complex of specific character is formed 1 . This pro- 
tein complex may act as a sensitizer, and upon subsequent injection of 
the drug there occurs a combination with blood proteins to produce 
a similar complex which reacts with the sensitizer to produce symptoms. 
Bruck and Klausner claimed to be able to sensitize guinea-pigs passively 
with the blood of susceptible patients, so that the animals reacted with 
the symptoms of anaphylaxis. The autopsies on these animals failed 
to show the characteristic findings of anaphylactic shock. Cole studied 
patients sensitive to iodides and to copaiba but failed to obtain results 
justifying the conclusion that the phenomenon should be included among 
anaphylactic manifestations. Specific cutaneous reactions to such drugs 
as quinine and aspirin have been described, and it is maintained that 
small doses by mouth may desensitize, but no widespread confirmation 
has been recorded. None of the drugs studied is without some essential 
toxicity and the idiosyncrasies in some instances, according to Sollmann, 
" are doubtless due to differences in the strength or constituents of 
drugs." He further states in regard to increased susceptibility that it 
" may be due to very rapid absorption, or slow elimination ; to the 


presence of synergistic substances in the body; or to increased func- 
tional susceptibility." 

The Tuberculin Test. In the course of his studies on the treatment 
of tuberculosis, Koch devised the method of diagnosis which we now 
speak of as the general tuberculin reaction, in contrast to the local 
reactions subsequently discovered. It is now known that the introduc- 
tion of tuberculin into the body may lead to local reactions both at the 
site of inoculation and in the neighborhood of a tuberculous focus as 
well as a general reaction which manifests itself in fever, headache 
and malaise. Numerous methods of preparation of tuberculin for 
therapeutic and diagnostic purposes have been described, but at the 
present time the diagnostic methods, in 1 the hands of the majority of 
workers, depend upon the use of original or old tuberculin of Koch. 

For the preparation of this tuberculin now designated as tuberculin O. T. 
the organisms are grown for six to eight weeks on the surface of 5 per cent, 
alkaline glycerine broth at 37 C. At the end of this time the entire contents 
of the flask are sterilized and concentrated to about one-tenth of the original 
volume by means of a current of live steam and a water bath. The glycerine 
does not evaporate, and as a result of the concentration constitutes 50 per cent, 
of the final mass. This is filtered through porcelain and the filtrate employed. 
Koch subsequently made other preparations, particularly the tuberculin 
known as T. R. and that known as B. E. The T. R. or tuberculin residue is 
prepared by growing virulent tubercle bacilli on nutrient glycerine broth for 
four to six weeks at 37 C. The bacilli are obtained by filtration, dried, and 
ground in a mortar. One gram is washed with 100 c.c. distilled water, the 
precipitate is again dried, powdered and repeatedly washed in small volumes 
of water until no sediment results. The watery extract constituted by this 
second series of washings, which should not exceed 100 c.c., is preserved with 
20 per cent, of glycerine and constitutes the T. R. The bacillus emulsion 
(B. E.) is prepared by growing the organisms as indicated in the preparation 
of the original or old tuberculin. The bacilli are obtained by filtration, ground 
in a mortar and emulsified in 100 parts of distilled water to which is added an 
equal amount of glycerine. 

Numerous other methods of preparing extracts of the tubercle 
bacillus have been described but are, in essential, modifications of 
the methods of Koch. At the present time the original or old tuber- 
culin is used most widely. 

The General Reaction. As a general rule, the old tuberculin is put on 
the market in the form of ampoules of fluid, i.o c.c. of which represents i.o 
gram of pure tuberculin. This may be diluted for the actual test. Inasmuch 
as individual sensitiveness varies considerably, the primary dose should be 
very small. According to Hamman and Wolman, three classes of patients 
may be recognized, (a) children, (&) patients who have a slight fever or are 
not in good general condition, (c) patients in good condition. The smaller 
doses are given to children and the largest dose to patients in good general 
condition. Upon this basis the initial dose of old tuberculin should be 
0.000,000,1 c.c. to 0.000,001 c.c.; failing to obtain reactions with these doses, 
subsequent tests may be made at intervals of about a week, increasing the 
dose each time. Although it is possible to give a maximal dose of i.o c.c. of 
the dilution, it is rarely advisable to exceed 0.05 c.c. The injections should 
be given under strict aseptic precautions, and appear to be most satisfactory if 
given at the lower angle of the scapula. They are probably best given in the 
afternoon, after the patient's afternoon temperature has been taken, so as 
to avoid the confusion of an unusually high elevation of temperature on the 
day selected. The reaction appears as a rule in from twenty-four to thirty- 
six hours. It may appear as late as forty-eight to sixty hours. A positive 
reaction is indicated by an elevation of temperature of about 2 to 4 C. In 


addition there is likely to be headache, malaise, and sometimes a loss of 
weight. At the site of inoculation there may be pain, tenderness, redness, 
swelling, sometimes associated with tenderness and enlargement of the 
regional lymph nodes. The contraindications to the employment of the test 
include the presence of fever, if fairly high and continued, nephritis, gen- 
eralized miliary tuberculosis, intestinal ulceration, epilepsy, acute infectious 
diseases, either during the course of the disease or its convalescence. 

The Cutaneous Reaction. Von Pirquet, who first described this modifi- 
cation of the tuberculin test, originally recommended the use of 25 per cent, 
solution of the old tuberculin, but subsequently found that the undiluted 
material is more suitable. He recommends the inner (flexor) surface of the 
forearm, and suggests the use of three points of scarification about 4 to 5 cm. 
apart. The skin is cleaned with ether or alcohol before making the abrasions. 
These may be small scratches with a needle, a knife or with an instrument 
which he describes as a borer, which has a sharp chisel point and is rotated 
in order to make a small circular abrasion. A drop of tuberculin is rubbed 
into the upper and lower abrasions; the middle one remains as a control. In 
positive cases, the reaction about the point of inoculation is considerably 
greater than that about the control point. The traumatic reaction in the 
control may reach a diameter of 3 to 5 mm. in twenty-four hours and then 
rapidly disappears. The positive reaction usually appears within twenty-four 
hours, but may be somewhat delayed. Its diameter is ordinarily about 
10 mm., but may reach 30 mm. It appears as a red, somewhat tender papule, 
which in severe reactions may show small vesicles. According to Kolmer, it 
is not to be interpreted as positive unless its diameter exceeds by 5 mm. that 
of the control. Occasionally the so-called scrofulous reaction appears, in 
which papules develop upon other parts of the extremities and the trunk. 

The Intracutaneous Tuberculin Tests. This was described by Mendel 
and also by Mantoux. For this purpose old tuberculin is injected into the 
cerium in doses whose bulk is 0.05 c.c. Two injections are necessary, one 
with salt solution and the other with tuberculin. The injection of tuberculin, 
however, may include three doses of different strengths. The reaction is 
very similar to that of the cutaneous test. Following a subcutaneous tuber- 
culin test, a similar reaction may appear in the track of the needle. 

The Percutaneous Tuberculin Test. This test was devised by Moro and 
Doganoff and is frequently spoken of as the Moro skin test. For this pur- 
pose 5.0 c.c. of old tuberculin are thoroughly mixed with 5 grams of anhydrous 
lanolin. This may be preserved for a long time in a light-proof container in 
the refrigerator and may be obtained on the market in collapsible tubes. 
About 0.5 gram of this ointment is rubbed into the skin of the abdomen, or 
breast near the nipple, rather vigorously for one minute. The reaction usually 
appears within twenty-four hours, but may be delayed from four to six days, 
and it subsides in three to ten days. It usually appears as a number of small 
papules reddened at the base. In severe cases the papules may become con- 
fluent and vesicles may form. 

The Conjunctival Tuberculin Reaction. This is also referred to as the 
ophthalmo-reaction and was described independently by Calmette and Wolff- 
Eisner. Calmette recommended a special aqueous extract of the bacilli but 
at the present time the test is usually applied with a I per cent, solution of 
old tuberculin. One drop of this solution is instilled into the conjunctiva 
near the inner canthus. The opposite eye serves as a control. Even in 
normal individuals the instillation may induce a slight reddening of the 
conjunctiva within six hours, but the positive reaction appears in from six to 
eight hours, reaches its height in from twenty-four to forty-eight hours, and 
then subsides in a few days or a week. The reaction may include simply a 
slight reddening and swelling of the caruncle, including the neighboring 
part of the lower lid, may extend over the scleral conjunctiva or may lead 
to a purulent conjunctivitis. Following the introduction of this test, unfavor- 
able reports were made because of the seeming danger of producing perma- 
nent injury to the eye, but Hamman and Wolman state that this danger is 
not considerable, provided proper precautions are taken in the selection of 
patients. Diseases of the eye or of the skin near the eye, obvious scrofula in 
children, and arterio-sclerosis are contraindications. The test should never 
be applied twice in the same eye, and no stronger solution than I per cent, 
should be employed for the first test. If the first test is negative a 5 per cent, 
solution may subsequently be employed in the opposite eye. 


Theories of the Tuberculin Reaction. Koch is of the opinion that 
the amount of tuberculin introduced when added to that already present 
in the body provides a sufficient amount of toxic substance to produce 
a definite general reaction. Koehler and Westphal thought that a 
toxic body is formed in the tuberculous focus by the union of tuberculin 
and the products of the tubercle bacillus. Marmorek suggested that 
the tuberculin excited the tubercle bacilli to produce in excess those toxic 
bodies which lead to fever. Von Pirquet and Schick were the first to 
suggest that this is a phenomenon related to hypersusceptibility. This 
conception fits very well the view of the relation of anaphylaxis and 
immunity which we have indicated above (page 226). Individuals who 
have markedly active tuberculosis are not likely to react, whereas those 
who have quiescent or cicatrized lesions almost always react. If the 
presence of tuberculosis leads to the formation of a sensitizing sub- 
stance, this can well be absorbed by the cells and be responsible for the 
local and general reactions. The tuberculin, upon local application, 
may react with a sensitizing substance in the situation concerned, or 
upon entrance into the circulation may similarly react with the sensitiz- 
ing substance in more widely distributed cells, thus producing a general 
reaction similar in principle to anaphylactic shock. If, on the other 
hand, the tuberculous process is so active that immune bodies can be 
found in the circulating blood, combination may be effected in that situ- 
ation and the cells protected. The study of complement fixation in 
tuberculosis indicates that this latter assumption is true, namely, that 
those who have active tuberculosis are more likely to react positively 
by the complement-fixation test, thereby indicating the presence of cir- 
culating antibodies in the active stages of the disease. 

Krause has studied this problem extensively, particularly in experi- 
mental animals and finds no reason for associating skin hypersensitive- 
ness and anaphylaxis. The anaphylactic state may be induced in 
animals by parenteral injection of tuberculo-protein, but they do not 
acquire cutaneous hypersensitiveness. Only by establishing a focus 
of infection, is it possible to demonstrate a skin reaction. Although 
during the period of anaphylactic shock an animal may appear to be 
somewhat less resistant to infection, the state of anaphylaxis produces 
no alteration in its resistance. Krause is of the opinion that tissue and 
cutaneous hypersensitiveness and immunity to infection occur under 
the same conditions, and that one may probably be a function of the 
other. In the experimental animal the degree of cutaneous hyper- 
susceptibility and immunity parallel each other. He suggests that the 
local reaction may also appear in the neighborhood of foci of infection 
and thus aid in walling off the infecting agent. Krause's opinion, 
based on much admirable work, is worthy of the highest consideration, 
but in so far as we can determine, it is not in accord with studies of 
immunity and cutaneous reactions in many other conditions, as pointed 
out in our discussion of cutaneous hypersusceptibility in general. Peter- 
sen considers the tuberculin reaction as a two-phase phenomenon. The 
primary alteration of the ferment-antiferment balance brings about a 


medium favorable for proteolysis in and about the tubercle. Digestion 
and the liberation of toxic material result and are reflected in the con- 
stitutional effects. In the non-tuberculous individual it is probable 
that the primary serum alterations also occur, but the digestive ferments, 
finding- no focus to attack, liberate no toxic material and no general 
reaction is elicited. Any agent that brings about a f erment-antif erment 
ratio favorable for proteolysis will effect a general reaction provided 
the focus be sufficiently unstable. Conditions such as pregnancy, acute 
infections, protein shock, in which there is an increase of antiferment, 
will inhibit the reaction. In late stages of tuberculosis there is also 
increased antiferment and therefore less marked local reactions but 
more marked general reactions. 

Specificity of the Tuberculin Reaction. The tuberculin tests have 
probably been more carefully controlled by autopsy than any of the 
other clinical tests, and we therefore are able to state with considerable 
assurance that a positive reaction indicates the presence of tuberculosis 
in the vast majority of cases, but, on the other hand, gives no very 
precise information as to the degree of activity of the process. Factors 
of error are more particularly found in the personal equation of the 
examiner. Leprosy and actinomycosis, however, may give confusing 
results. In a very large series of tests, more than 15,000, the percentage 
of error is very small, varying from 2 to 3 per cent. Negative reactions 
may appear in markedly active tuberculosis, in the very early stages of 
the infection, in those small cicatrized lesions of the lung so firmly 
encapsulated that no absorption takes place, during continued treatment 
with tuberculin; also during the course of measles, typhoid fever, 
acute articular rheumatism, pneumonia, diphtheria, pertussis, serum 
disease and during pregnancy. 

Some authors have such confidence in the specificity of the tuber- 
culin reaction that they consider it possible to determine the strain of 
the organism concerned, but others deny that this delicacy is attainable. 
The recent work of Petersen would indicate that there is a large non- 
specific element in the tuberculin reaction. Tuberculous patients may 
react to the following substances with local and even general reactions : 
hypertonic salt solution, distilled water, iodides, some colloidal metals, 
protein split products, etc. Non-tuberculous individuals will tolerate 
equal doses without reaction. The relation of this type of reaction to 
the true test has been indicated in discussion of the theories of the 
tuberculin test. 

Utility of the Tests. At the present time in clinical practice the 
subcutaneous or general reaction is not very widely employed, because 
of the prejudice that has been aroused by the possibility of exciting the 
lesion to renewed activity. Similarly a prejudice exists somewhat 
unjustly against the use of the conjunctival reaction. Although Ham- 
man and Wolman indicate that the intracutaneous test is the most sensi- 
tive, our observation is to the effect that the cutaneous test is most 
widely employed. It is simple, free from danger, well controlled, 


easily read and is sufficiently sensitive to provide all the information that 
can reasonably be expected to accrue from the tuberculin test. 

Luetin Reaction. Numerous attempts were made following the 
announcements of the Von Pirquet cutaneous tuberculin test, to devise 
a similar test for syphilis. It was found, however, that extracts of 
normal organs produced the same effects as those from syphilitic organs. 
It was not until Noguchi cultivated the treponema pallidum in vitro that 
a preparation of the causative agent could be prepared. Noguchi pre- 
pared a suspension of the organisms together with the ascites-kidney 
agar upon which they were grown. Cutaneous reactions were unsat- 
isfactory, and it was found necessary to make the test by intracutaneous 
injection of the material. The reaction appears in papular or pustular 
form in from twenty-four to forty-eight hours or later. It was found 
by Sherrick that patients receiving potassium iodide give positive reac- 
tions and by Cole and Paryzek that similar reactions follow the ad- 
ministration of bromides. Although Noguchi found that injection of 
the culture medium without the organisms did not produce reactions, 
Stokes as well as Kolmer, Matsunami and Broadwell were able to pro- 
duce reactions by injecting agar. Although Noguchi and others re- 
ported high percentages of positive reactions in known syphilitics, yet 
in the hands of some workers the number has been only about 50 per 
cent. The test is not widely employed and apparently gives no informa- 
tion that cannot be obtained equally well or better from the Wasser- 
mann test. It has been suggested that the luetin test may be of value 
in late syphilis, where the Wassermann test is negative, but the large 
non-specific element of this skin reaction does not tend to place much 
reliance upon the test. 

Cutaneous Reactions in Typhoid Fever. Several of the earlier 
studies on this subject were concerned with reactions in the conjunctiva. 
Chatemesse and also Austrian were able to obtain positive ophthalmo- 
reactions in a large percentage of cases of typhoid fever and prac- 
tically no positive reactions in other individuals. Although Kraus could 
not obtain skin reactions, Zupnik and also Floyd and Barker obtained 
encouraging results. Gay and Force have employed a substance which 
they name typhoidin, prepared from bacillus typhosus, according to the 
method employed for the preparation of old tuberculin. The prepara- 
tion was modified subsequently by Gay and Claypole. The typhoidin 
is applied in abrasions of the skin as with the cutaneous tuberculin test. 
These investigators found a high percentage of positive reactions in 
individuals who had recovered from typhoid fever as well as those 
who had been vaccinated and recommend it as a method for determining 
the presence of immunity to typhoid fever. Kilgore has studied the 
test clinically and finds that the test is unreliable because of unavoidable 
variations in the application of the test, indefiniteness of the readings 
and the large non-specific element in the reaction. 

Cutaneous Reactions to Gonococcus Infections. These reactions 
are particularly applicable to deep-seated and chronic infections with 
the gonococcus. Irons found local and general reactions following the 


subcutaneous injection of gonococcal vaccine and subsequently pre- 
pared a glycerol extract of the organism for cutaneous tests. He 
instituted controls with equal quantities of glycerol and obtained dis- 
tinctly encouraging results even to the point where one strain of or- 
ganism produced stronger reactions than other strains. 

Cutaneous Reactions to Meningococcus Infections. Recently Gay 
and Minaker have employed the intracutaneous reaction for the detec- 
tion of meningococcus carriers. They prepared a salt solution emulsion 
of carefully washed and thoroughly dried cultures of five strains of 
meningococcus and injected 0.000,006 gram of the dried powder in a 
total volume of 0.05 c.c. They obtained reactions in 64.5 per cent, of 
known carriers and 26.4 per cent, in individuals known not to be 
carriers. They do not think that the reaction serves any important 
purpose in diagnosis but suggest that it may indicate a systemic reaction 
and possibly a certain degree of acquired resistance to the organism. 

Cutaneous Reactions to Pneumococcus Infections. Earlier in- 
vestigations with salt-solution extracts were not particularly satis- 
factory in regard to the early diagnosis of pneumonia, although after 
the crisis reactions were obtained. Weiss and Kolmer prepared a 
solution of Type I pneumococci in sodium choleate which they designate 
pneumotoxin. The test is performed by intracutaneous injection. By 
careful study of animals, on the basis of both gross and microscopic 
examination of the site of reaction, as well as of human patients with 
pneumonia, they obtained distinctly encouraging results during the 
course of the disease and state that although the test does not seem 
to be of distinct value in differentiating the type of organism con- 
cerned, yet it may aid in differential diagnosis between appendicitis, 
tuberculosis and pneumonia. 

Cutaneous Reactions to Vaccine Virus. Jenner noted that in cer- 
tain individuals who had previously been vaccinated against smallpox, 
a second vaccination might produce a local reaction which did not go on 
to produce vaccinia. This has been observed by numerous investi- 
gators since then and Force has given the subject close study. For 
this purpose Force produced three abrasions on the arm, into two of 
which vaccine virus was rubbed and made observations at the end of 
twenty-four, forty-eight and seventy-two hours. " If either of the vac- 
cinated spots showed an areola of 5 mm. or over (with or without 
papule) at the end of twenty-four hours, which areola (or papule) had 
decreased at the time of the seventy-two-hour observation, it was con- 
sidered a reaction of immunity due to the presence in the blood of the 
individual of antibodies against vaccine virus." " If either of the vac- 
cinated spots showed an areola at the end of twenty-four hours which 
developed into a small vesicle, maturing on the fifth or sixth day and 
then rapidly subsiding the reaction was considered a vaccinoid," a con- 
dition in which it is supposed antibodies are not present but are rapidly 
formed because of a previous vaccination, thus leading to the small 
size and rapid subsidence of the vesicle. " If there was no change until 
the third day, and then a small areola began to form, the case would be 


vaccinia." This description indicates the changes that may appear fol- 
lowing an uninfected vaccination with smallpox virus. There appar- 
ently occurs, following smallpox and vaccinia, an altered state which 
determines these local reactions, but the interpretation offered by Force 
that some of these reactions are immune reactions still lacks satis- 
factory confirmation and is not consistent with other studies of 
cutaneous reactions (see page 237). 

Cutaneous Reactions in Glanders. The Mallein test devised by 
Kelmann and Kelming is widely employed in veterinary practice, either 
in the form of subcutaneous injection which produces a general reaction 
as is the case with tuberculin, or in the form of conjunctiva! test which 
produces local and often general reactions. 

Other Cutaneous Reactions. As can very well be understood the 
encouraging results with such a large number of skin reactions has 
led to the investigation of similar tests in other diseases and the reac- 
tion has been applied in leprosy, sporotrichosis, hyphomycetes infec- 
tions, pregnancy, canine distemper and numerous other conditions. 
The Schick test for diphtheria is not to be included among the skin 
reactions indicating hypersusceptibility, for, as has been shown pre- 
viously, this test depends upon the presence or absence of antitoxin in 
the circulating fluids of the body. 






Introduction. The relation of ferments to immunity and ana- 
phylaxis has long been the subject of discussion. In the chapters on 
special immune bodies we have discussed the. similarities and differences 
between ferments or enzymes and antibodies. Special consideration has 
been given to certain phases of ferment activity, particularly in the 
chapter on Cellular Resistance and that on Hypersusceptibility. Ap- 
parently the first work to prove that digestion takes place outside the 
intestinal tract was that of Hammersten, who showed in 1885 that 
washed leucocytes increase the solubility of fibrin. This was followed 
by more comprehensive studies on cellular ferments as have been pre- 
viously outlined (page 167). In addition to those ferments which exist 
in the cells, ferments have been discovered in the blood and other circu- 
lating body fluids. Therefore, we may classify the ferments as intra- 
cellular and extracellular. The scope of this book is too limited to 
permit of any general discussion of ferments as a group and the 
reader is referred to the sections on this subject in Wells' " Chemical 
Pathology." Many of the earlier workers assumed that ferments in 
the body fluids are derived essentially from the leucocytes. A recent study 
of considerable significance is that of Boldyreff. He maintains that the 
glands of the alimentary canal, with the exception of those of the 
stomach, are not at rest between the digestive periods and that they 
exhibit a periodic function. As a result of this periodicity, secretions 
are discharged into the empty intestine from which they are absorbed 
and at times are demonstrable in the blood. Van Calcar claims that 
the leucocytes are incapable of producing their own ferments and that 
these ferments are derived from special glands. He found that extir- 
pation of the stomach is followed by a decrease or absence of that 
ferment of the leucocytes which acts best in acid medium and that 
extirpation of the pancreas similarly is followed by a loss of tryptic 
powers on the part of the leucocytes. Abderhalden believes that invertin 
also is derived from the intestinal glands. This conception would indi- 
cate that the appearance of ferments in the circulating body fluids is to 
be regarded as a mobilization of ferments from the cells which 
formed them. 

Specificity of Ferments. It is well known that the body ferments 
act specifically upon certain chemical substances, as exemplified by the 



digestion of starch by amylase and of protein by pepsin. The question 
as to whether or not specificity in the immunological sense can be demon- 
strated has been the subject of much discussion. Claims have been 
made for specificity of ferments not only in regard to animal species 
but also in regard to specificity for the cells of particular organs. The 
chief proponent of the specificity of ferments for cells and proteins is 
Abderhalden. He was stimulated to this view by the work of Schmorl 
and others, who demonstrated that during pregnancy fragments of the 
syncytium of the chorionic villi often enter the circulation and by the 
claims of Weinland that specific reducing ferments are produced fol- 
lowing the parenteral introduction of cane sugar. Abderhalden there- 
upon examined the blood serum of pregnant animals and found that 
the serum contained a ferment capable of splitting placental pepton 
into amino-acids and of digesting coagulated placental tissue into pep- 
ton, polypeptids and amino-acids. These decomposition products are 
diffusible and also alter the axis of optical rotation of the mixture. The 
detection of the diffusible products of protein decomposition was made 
by means of " ninhydrin " or triketohydrindenhydrate, which reacts 
with alpha amino-acids so as to produce a blue or violet color. The 
practical application of a test of this sort is obvious and the method 
has been employed to detect specific ferments in pregnancy, in car- 
cinoma, in sarcoma, in diseases of the brain, of the eye and of numerous 
other organs. Practical experience with the test, as well as further 
scientific study, has made it seem probable that the specificity claimed 
by the Abderhalden school does not exist. This will be further dis- 
cussed in connection with the Abderhalden test. 

Immune Ferments. Numerous investigators have published re- 
ports indicating that the parenteral introduction of special sub- 
stances leads to production of special ferments or at least to an increase 
of preexisting ferments in the form of a mobilization. Delezenne re- 
ported in 1900 that the injection of animals with gelatine produces a 
blood serum capable of liquefying gelatine. Weinland in 1907 showed 
that although normal dog serum cannot reduce cane sugar the immuniza- 
tion of a dog by several injections of cane sugar leads to the formation 
of a ferment capable of reducing cane sugar in vitro. Similarly, im- 
munization with edestin produces a serum capable of splitting this 
substance. The more recent investigations of the subject would make 
it appear that the immunization leads rather to mobilization of non- 
specific ferments than to the production of a specific immune body. 

Ferments in the Blood. Wells states that the blood contains di- 
astase, glucase, lipase, thrombin, rennin and proteases. In addition, 
the blood possesses oxidizing properties due presumably to the presence 
of oxydase, peroxydase and probably also due to catalase. The pro- 
teases have been given particularly careful study. Petersen divides 
these ferments into the leucoproteases, serum proteases and serum pep- 
tidases. The leucoproteases include (a) an active ferment operating in 
alkaline medium and capable of digesting native protein to the proteose 
stage, (&) an active ferment capable of operating in acid medium with 


a similar range of activity, and (c) an ereptase active in both acid and 
alkaline media and capable of splitting partially hydrolized proteins into 
amino-acids. Of these ferments only the ereptase is able to act in the 
presence of blood serum and tissue fluids because the others are inhibited 
by the activity of antiferment constantly present. The serum protease 
is a polyvalent trypsin-like ferment active in neutral, in slightly acid, 
or in slightly alkaline media; it is completely inhibited by the antifer- 
ment of the circulating fluid. It becomes active only when the anti- 
ferment is removed and is capable of digesting native protein to the 
amino-acid stage. It is present in fairly large amounts in sera of the 
lower animals, but is found in only small quantities in human serum. 
The serum peptidase is a polyvalent ferment which operates in the 
same type of media as the protease ; it is present in normal human serum 
in small amounts, is not inhibited by antiferment and digests partly 
hydrolized proteins to the amino-acid stage. Since the toxic fractions 
of proteins are principally in the form of proteoses and pepton, the 
peptidase apparently is the most important ferment in destroying such 
toxic bodies. 

The importance of esterases in the blood is not at all clear. It is 
known that lymphocytes contain a lipase, and it has been suggested 
that the accumulation of these cells about tuberculous foci may indicate 
the importance of this ferment in breaking down the waxy capsule of 
the bacilli. Jobling, Petersen and Eggstein recommend the following 
methods for the determination of serum protease and serum esterase 
(Journal of Experimental Medicine, vol. xxii.). 

" The technic for proteases is as follows : The clear hemoglobin- free serum 
is measured with an accurate i.o c.c. pipette into a rather wide test-tube (about 
18 mm.). To the tube 0.5 to 0.75 c.c. of chloroform is added and the tube is 
sharply shaken, at intervals, until a milky emulsion is formed. We prefer chloro- 
form because the 'emulsion is more stable than with ether or other lipoid solvents. 
A control tube is inactivated at 60 C. for thirty minutes and a drop of toluol is 
then added in place of chloroform. Both tubes are then incubated over night 
(fifteen to sixteen hours at 37). In the morning about i.o c.c. of a mixture 
of 10 per cent, acetic acid plus 20 per cent, salt solution is added, and the tubes 
are then gently warmed in a water bath until the chloroform has been evaporated. 
About 2 or 3 c.c. of distilled water are then added slowly and the tubes boiled 
for at least ten minutes. The coagulated protein is filtered off by means of 
hard filter paper, previously moistened, the filtrate being permitted to ^ filter 
directly into the large tubes used for oxidizing. The tubes are then oxidized 
and Nesslerized according to the usual Folin method, the readings being made 
against varying dilutions of the i mg. standard, so that test readings are made 
against standard of apparently equal color." 

" Serum esterase has been determined as follows : To i.o c.c. of the serum, 
i.o c.c. of neutral, redistilled ethyl butyrate and 0.5 c.c. toluol are added, the 
volume being brought to 10.0 c.c. with physiological salt solution. The flasks 
are then shaken 100 times and incubated for four hours ; 25 c.c. of neutral 95 per 
cent, alcohol are then added to each flask and the acidity which has developed is 
titrated with N/5O sodium hydrate (alcoholic) to a faint pink with phenolphtha- 
lein. After deducting the proper controls, i.e., serum alone, ethyl butyrate alone, 
etc., the esterase index is expressed in terms of c.c. of N/ioo sodium hydrate used to 
neutralize the acidity developed by i.o c.c. of serum from i.o c.c. of ethyl butyrate." 

Ferment-Antiferment Balance. The activity of various ferments 
in the body is probably effective in various degrees at all times, and 
this activity probably plays a certain part in normal metabolism. Cer- 


tain of the ferments become active only when suitable material is pre- 
sented, as is the case with the serum peptidase; others operate only 
when the surrounding medium reaches suitable reaction; still others 
operate only if the antiferment content is sufficiently reduced. There- 
fore, the preservation of the body tissues against destructive action of 
ferments and the normal processes of metabolism depend in considerable 
part upon the neutralizing activity of antif erments. 

Antiferment. Certain investigators have reported the production 
of specific antibodies following the injection of ferments. Morgen- 
roth claimed to have produced a specific antirennin, Sachs and Achalme 
an antipepsin and an antitrypsin, Schultze an antisteapsin and an 
antilactase, Gessard an antityrosinase and Moll an antiurease. The 
recent studies of antif erments, however, indicate that inhibitory activity 
is not specific and this subject has been contributed to particularly by 
Jobling and his collaborators. They are of the opinion that anti- 
f erment activity depends upon the highly dispersed unsaturated lipoids 
of the serum and lymph and that the titer varies with the amount of 
lipoids, their dispersion and chemical structure. In studying anti- 
trypsin, they found that the inhibitory substances are of the nature 
of soaps and that the ability to inhibit ferment activity depends upon the 
degree of unsaturation of the carbon bonds in the fatty acid. They 
made soaps from olive oil, cod-liver oil, linseed and other oils and 
found that these soaps inhibited the action of trypsin and leucoprotease. 
They determined further that extraction of the blood serum with such 
fat solvents as chloroform and ether removes the antitryptic activity. 
Soaps prepared from the extracts restored the antitryptic activity. The 
serum residue, after extraction, was found to be highly toxic for 
guinea-pigs. If, however, the soap prepared from the extract were 
added to the residue, the toxicity was neutralized. Jobling and his 
collaborators attributed the toxic action of the serum residue to (a) 
alteration of the mechanism of intravascular coagulation, (&) exposure 
of native serum proteins to the action of ferments and (c} the resulting 
formation of toxic split products. These workers isolated unsaturated 
fatty acids from tubercle bacilli and found that when these were sapon- 
ified they inhibited the action of trypsin but lost this power when satur- 
ated with iodine. They were able to obtain similar soaps from caseous 
lymph-nodes and suggest that the soaps prevent the activity of ferments 
which would normally digest the necrotic material. This failure of 
digestion leads to the formation of the partly-digested and fatty sub- 
stance which is spoken of as the caseation necrosis. 

The antif erments are greatly augmented in certain diseases, such as 
acute infections, carcinoma, cachexias in general, anaphylactic shock, 
certain degenerative changes of the nervous system and in pregnancy. 
Jobling explains the crisis of pneumonia as being due to an alteration 
in the f erment-antiferment balance ; that there is a decrease in the anti- 
ferment with a corresponding mobilization of protease, an increase in 
the serum lipase with a resulting decrease in the non-coagulable nitrogen 
and proteoses of the serum. 


Determination of Antiferment in Blood Serum. The determination of 
antitrypsin by the Fuld-Gross method is satisfactory for this purpose. This 
requires in addition to blood serum taken preferably in the morning before 
the patient's breakfast, solutions of casein, acetic acid, and trypsin. The 
solution of casein is made by dissolving i gram casein in 100 c.c. N/io NaOH 
with the aid of slight heating; the solution is neutralized with N/io NaCl and 
made up to 500 c.c. with 0.85 per cent. NaCl. The acetic acid solution is made 
by mixing 5.0 c.c. acetic acid with 45.0 c.c. alcohol and 50.0 c.c. water. The 
trypsin solution is made by dissolving 0.5 gram trypsin (Griibler) in 50.0 c.c. 
0.85 per cent. NaCl and 0.5 c.c. normal soda solution; this is diluted ten times 
with saline. The patient's serum must be fresh and should be diluted with 
salt solution so as to make a 2 per cent, solution. 

The trypsin is titrated as follows: Place in a series of test tubes o.i, p.2, 
0.4, 0.6, 0.8, and i.o c.c. of the trypsin solution. Add 2.0 c.c. of casein solution 
to each tube, shake and incubate for one-half hour at 50 C. Add three or 
four drops of the acetic acid solution to each tube and note the precipitation 
(cloudiness) which appears in the course of a few minutes. The tube which 
remains perfectly clear contains enough trypsin to digest 2.0 c.c. of the casein 
solution. For testing the antitryptic content of the serum add 0.5 c.c. of the 
2 per cent, solution of serum to each of six small test tubes. Then add to 
each tube in series, increasing amounts of the trypsin solution, beginning with 
the largest dose that completely digested the casein, and increasing in each 
tube by o.i c.c. Add 2.0 c.c. of casein solution to each tube and make up to 
equal volumes with normal saline. Shake and incubate for one-half hour at 
50 C.; then add three or four drops of the acetic acid solution to each tube 
and observe as before. The amount of trypsin which is inhibited by the 
serum is determined by the lack of complete digestion, as shown by the acetic 
acid precipitation. A control series should be set up with the pooled sera of 
normal individuals. Jobling and his associates made the test somewhat more 
accurate by filtering after the incubation and then determining quantitatively 
the non-coagulable protein nitrogen. 

The Abderhalden Test. In the discussion of the specificity of fer- 
ments, we pointed out that Abderhalden had assumed that the entry of 
cellular and other proteins in the circulation could lead to the formation, 
or increase, of ferments which have as their specific character the prop- 
erty of digesting the antigenic protein. The test is based fundamentally 
upon a mixture of serum and antigenic substance and the determina- 
tion of the formation of diffusible protein products. He regarded the 
ferments as protective, inasmuch as they could break down and aid 
in the elimination o>f substances essentially foreign in nature. The 
technic of the test has been carefully reviewed by Bronfenbrenner in 
Vol. I of the Journal of Laboratory and Clinical Medicine, and we call 
particular attention to certain modifications that have been offered by 
Retinger in Volume XXII of the Archives of Internal Medicine. The 
following brief description of the test is given in order to provide an 
outline of the general principles. 

The materials essential for the test are the serum or plasma of the 
patient, the substratum, dialyzing tubes and flasks, carefully distilled water, 
clean test tubes and ninhydrin. The blood is withdrawn before the patient's 
breakfast in order to obtain blood at a time when no dialyzable products of 
intestinal digestion are present. It may be taken into paraffin-coated centri- 
fuge tubes for the preparation of plasma or may be allowed to clot and 
the serum centrifuged so as to be absolutely clear. The substratum is the 
material to be digested. As a rule, the tissue is cleared of connective tissue 
in so far as possible, is perfused with salt solution and subsequently washed 
several times with distilled water until it is absolutely free from blood. It is 
then placed in a suitable container, coagulated by boiling, and repeatedly 
washed with boiling water until the fluid gives no ninhydrin test. It is then 


preserved under toluol. The dialyzing thimbles are especially prepared for 
work of this kind. They are kept in distilled water for at least a week and 
are carefully tested before use so as to be sure that protein does not pass 
through and also to be sure that pepton will pass through. For the actual 
test a dialyzing thimble is placed in a clean, dry, sterile Erlenmeyer flask. 
About 0.5 gram of dried substratum is placed in the bottom of the thimble 
and 1.5 c.c. of serum then introduced. The thimble is withdrawn, closed at 
the top by means of a forceps and the outside washed carefully with sterile 
water so as to remove any adherent protein. The thimble is then replaced in 
a flask containing about 20 c.c. sterile distilled water. The contents of the 
thimble and the water in the flask are covered with toluol and the flask 
incubated for sixteen to eighteen hours. The dialyzate is examined by 
means of the ninhydrin test. For this purpose, 0.2 c.c. of i per cent, ninhydrin 
solution is placed in a clean dry test tube and 10.0 c.c. of the dialyzate added, 
the mixture boiled for one minute and the color observed. The development 
of a blue or violet color indicates the presence of diffusible protein products 
and constitutes a positive test. Proper controls of all the reagents are essential. 

Since the earlier work of Abderhalden appeared, numerous articles 
have been written and there has been much discussion concerning the 
alleged specificity of the reaction. The protective ferments of Abderhal- 
den are assumed to possess the property of directly digesting the antigen 
and the appearance of the products of such direct digestion constitutes 
the fundamental principle of the Abderhalden test. Stephan, Haupt- 
mann, Bronfenbrenner and others have shown that these ferments lose 
their activity after heating to 58 C. for one-half hour, but they can 
be reactivated by the addition of fresh serum. This suggests a parallel 
with the activity of complement and amboceptor, but Frank and Rosen- 
thai point out that in hemolysis there is no indication that the action 
of complement is accompanied by proteolysis. Therefore, although the 
ferment may be reactivated after heating, this does not necessarily 
indicate that it is of the nature of an amboceptor or other immune 
body. Flatow, Plaut and others have reported that positive results 
can be obtained by the manipulation of material and that positive or 
negative reactions can thus be found with almost any serum. De Waele 
found that he could demonstrate a digesting substance within a few 
minutes after the parenteral introduction of foreign protein, a time 
interval too short for the production of specific ferments. Heilner and 
Petri regard this, however, as a sort of mobilization of ferment and not 
the result of new formation. Bronfenbrenner found that the serum of 
highly immunized animals failed to digest the protein used for im- 
munization. He determined, however, that such a serum gave a positive 
Abderhalden test and with his collaborators has demonstrated that the 
dialyzable substances do not originate from the substratum. He showed 
also that the ferments responsible for the cleavage of protein during 
the reaction are not specific. Positive results with placenta are to be 
obtained with the serum of males as well as of females, but the protein 
digested is that of the serum. The work of Jobling and his collabor- 
ators favors the view that proteolytic activity of the serum is not 
specific. Plaut, Bronfenbrenner and others found that positive 
Abderhalden tests may be obtained by the use of kaolin, starch, barium 
sulphate and chloroform, all of which probably absorb the inhibiting 
substance or antiferment of the blood. Van Slyke and his associates, 


by means of determining the amino-nitrogen, found that practically every 
serum shows some degree of protein digestion when incubated with 
placental tissue. Van Slyke's methods are so accurate that it seems 
probable that the ninhydrin tests with dialyzates must vary consider- 
ably, depending upon the amount of dialyzable substance which may 
pass through any given thimble. Elsesser worked with the purified 
vegetable proteins of Osborn and found that at best the specificity of 
the reaction is less than that of anaphylaxis and that there are many 
non-specific results. Boldyreff found that the ferments act not only 
upon placental proteins but also upon other varieties of protein; he 
believes that the method is excellent for detection of proteolytic enzymes 
in the blood but as a distinctive sign of pregnancy it is useless. Against 
these views are the recent results of Retinger, who claims that it is 
not only possible to demonstrate lesions of the brain by this test but 
further to define within fairly small limits the localization of the 
lesion. It may be that with further modifications a test of some clini- 
cal value can be developed upon the basis of the Abderhalden test. At 
the present time, there is little reason for accepting the conception of 
specific ferments and the test has been entirely discarded in 
many laboratories. 



















THE development of immunology has resulted in extensive study 
of the treatment of disease by sera prepared according to a variety of 
methods. We have considered in other chapters the value of certain 
sera, more particularly those which possess a demonstrable content of 
antitoxin. In this chapter there is presented a brief statement as to the 
methods of preparation and use of other types of sera with the idea 
of illustrating how widely this form of therapeusis has extended and 
the principles upon which the methods are founded. Certain of these 
sera have given excellent results, t>ut others have failed utterly and still 
others are yet in the stage of experiment and investigation. The judg- 
ment as to the value of many of the sera rests upon statistical evidence 
collected on a clinical basis. The use of man for investigation intrudes 
into the results obtained a wide variety of sources of error, many of 
which can be excluded in investigations upon the lower animals. Dif- 
ferences in hygienic surroundings, conditions of exposure, presence of 
diseases other than that treated, differences in weight, age and sex 
must all be considered. The stage of increase or decrease of the epi- 
demic must be included in the final judgment since the virulence of 
infections is likely to be greater at the beginning of an epidemic than 
during its decline ; this may be due to exhaustion of the causative agent, 
but is more probably accounted for in that the less resistant individuals 
succumb early in the epidemics and the more resistant are attacked sub- 
sequently. The factor of error in random sampling must be calculated 
as closely as possible and it must be recognized that the greater the 
number of cases studied, the more conclusive are the results. The 


. investigator is always actuated by the hope that the particular method 
he fosters will be of value in the alleviation of human disease, and 
this fact may determine a subconscious selection of cases and perhaps, 
equally subconscious, somewhat superior nursing and better care of the 
cases under special treatment than of the controls. Thus the analysis of 
statistical evidence must be made with rigid consideration of the various 
factors of error. Minor differences in percentages of cure or of im- 
provement may be within carefully computed factors of error and still 
not take sufficiently into account a considerable factor of error resulting 
from our ignorance of the intricacy of biological phenomena. 

Immune sera for therapeutic purposes have been prepared by the 
injection of bacteria, their toxic or non-toxic extracts, or by combina- 
tions of these substances. Some of these sera exhibit a variable content 
of antibodies of the first, second or third order of Ehrlich. The most 
important laboratory test, however, appears to be the protective value 
of the sera in preventing infection in animals or their curative value 
after the infection is established. There is no necessary parallel between 
the content of special antibodies and the protective or curative value, ex- 
cept in the case of antitoxic sera. Thus a serum may exhibit a low ag- 
glutinin or bacteriolysin content and yet protect animals when used in 
extremely small amounts. The converse is also true, namely, that rela- 
tively high content of agglutinin or bacteriolysin does not necessarily 
presuppose a great capacity for protection. Furthermore, it cannot be 
assumed positively that because animals are protected or cured, the 
serum will be of equal value in human medicine ; hence the necessity 
for carefully studied experiments on man. 

Not only have immune sera been employed, but many attempts at 
treatment of disease by means of normal sera have been made. This 
procedure is based in part upon the principles of non-specific immun- 
ological treatment which have been previously discussed. Such sera 
may be obtained from man, horse, goat, ox or other animal. In the 
treatment of certain hemorrhagic disease the purpose of the serum 
may be physiological rather than immunological, inasmuch as the serum 
is believed to provide certain essentials for the process of clotting which 
the patient provides in insufficient amounts or not at all. 

In the following discussion it will be noted that there are first taken 
up those sera prepared by immunization with bacteria; second, those 
prepared by immunization with bacterial extracts, either with or without 
the bacterial bodies; third, treatment with the patient's own serum; 
fourth, treatment with sera from convalescent human cases ; fifth, spe- 
cific serum therapy in diseases of unknown origin, and finally, treat- 
ment by normal sera. 


Anti-streptococcus Serum. The protection afforded by the use of 
streptococcus immune serum is still problematical. The reason for this 
lies partly in the fact that there are several different types of streptococci 
concerned in human infection. Some of the strains occur frequently and 


others only rarely. It is, therefore, advisable to determine as soon as 
possible the type of the organism, and then combat it with its special 
antiserum. Havens succeeded in dividing these organisms into three 
distinct groups by means of cultural and immunological examination 
and found that an immune serum can be produced for each of the three 
groups. The serum is specific for its own group and protects mice 
against infection with homologous organisms, but furnishes no pro- 
tection against infection with organisms from the other groups. From 
this work it is evident that the utilization of specific sera is of para- 
mount importance in the treatment of streptococcus infections. The 
oldest serum is that of Marmorek. This serum was produced by im- 
munization with a strain which was made highly virulent by animal 
passage and the serum was found to be protective experimentally when 
administered twelve to eighteen hours before the bacteria were injected. 
This serum was used in erysipelas, puerperal septicemia and scarlatinal 
angina with favorable results. Lenhartz, Baginsky, Zangemeister and 
others, however, failed to obtain definitely good results with anti-strepto- 
coccus sera. Sera were later produced by Aronson and Tavel, Van de 
Velde, Meyer, Ruppel, Menzer and Moser for use in puerperal sepsis, 
scarlatina, erysipelas and acute articular rheumatism. In puerperal 
infection a fresh polyvalent anti-streptococcus serum should be given 
daily in intravenous doses of 30. c.c. until marked improvement occurs. 
These cases are usually slow in improvement, but the results so far 
obtained seem to be encouraging. It is, however, of the greatest im- 
portance to introduce serum treatment at the earliest possible moment. 
In scarlatina Escherich found that if the serum be used on the first and 
second days of illness recovery of the majority of cases is likely to 
occur. Axenow, in fact, believes that it is the only means to ward off 
a fatal outcome. In erysipelas and acute articular rheumatism the 
results have been at variance. Park states that the injections should 
be made before the infection has become advanced and before the 
streptococci have acquired an increased resistance to the serum anti- 
bodies and ferments. The repeated local bathing of exposed infected 
tissues with the serum seems to have a beneficial result beyond that 
exercised by a non-specific serum. The action of anti-streptococcal sera 
is largely due to its opsonic powers. The hope for effective serum 
therapy in streptococcus infection is at present based on the new 
methods of serologic classification of the organism and further labora- 
tory and clinical study is highly desired. 

Anti-meningococcus Serum. In 1906 Jochmann for the first time 
treated cerebrospinal fever with serum of horses immunized to several 
strains of meningococci. This serum was highly agglutinative, some- 
what bactericidal, but not antitoxic. The death rate among the treated 
cases was 27 per cent, as compared to 53 per cent, among the non-treated 
cases. In the earlier work Jochmann administered the serum subcu- 
taneously but later advised its use by the intraspinal method. Almost 
simultaneously Flexner and Jobling carried out extensive work on 
monkeys. They demonstrated that the most beneficial effect of the 


serum follows intrathecal administration, and in 1907 successfully 
applied serum treatment of the disease during an epidemic in Akron, 
Ohio. The following table, taken from Worster, Drought and Mills 
Kennedy, " Cerebrospinal Fever," London, 1919, gives the results ob- 
tained by several investigators. 

No. c Serum Cases not 

Author of treated * i, m treated treated with 

cases mortality serum mortality 

Flexner . . 1294 (collected) Flexner 30.9% 70% 


Dunn . 

Robb . 


ioo Flexner 28.0% 49% 

40 Flexner 22.5% 70% 

300 =*= Flexner 30.0% 72% 

402 Dopter 16.4% 65% 

Levy 165 [ v^ssermann } l8 ' 8 ^ 52 % 

Steiner . . . 2280 (collected) 37 .0% 77% 

Schoene . . 30 Jochmann 30.0% 53% 

Although many English investigators have been successful in the use 
of anti-meningococcus serum, several experienced men have advised 
against its use. This is largely because of the fact that Gordon, Ellis 
and others have demonstrated several types or groups of the meningo- 
coccus, and it is believed that sera should be prepared against each 
type in order to obtain the best results. Rolleston has compiled the 
following table of results with various types of anti-meningococcus sera : 

Brand of serum Mortality Recoveries 

Flexner 22.3 per cent. 77.7 per cent. 

Gordon 18.7 per cent. 81.3 per cent. 

Pasteur Institute 44.5 per cent. 55.5 per cent. 

Burroughs-Wellcome ... 33.3 per cent. 66.7 per cent. 

Mulford 50.0 per cent. 50.0 per cent. 

Lister Institute 54.5 per cent. 45.5 per cent. 

Gordon's and Flexner' s sera have so far given the best results. It 
is advisable to test the agglutinative power of a serum prior to its use, 
using a strain freshly isolated during the epidemic. The serum should 
agglutinate the organism in a dilution of at least one to five hundred. 
The lack of a definite potency standard makes it impossible to judge 
accurately the value of any given serum. As in diphtheria and other 
diseases, the early use of serum is of the greatest importance. Flexner 
found that if the serum was given in the first three days the mortality 
was 1 8 per cent., if given from the fourth to the seventh day it was 
27 per cent., and if given later 36.5 per cent. Similar figures were 
obtained by Rolleston, Gray, Robb and Worster-Drought. If neces- 
sary, the injections should be repeated. According to Park, it is advis- 
able to give not less than four daily injections unless the case is already 
convalescent when it comes under observation. If the organisms or 
symptoms do not disappear, the injections of 10 c.c. to 25 c.c. of serum 
should be continued for many days. Finally, as a result of army experi- 
ence, Herrick believes that the disease is in most if not all cases a 
general bloodstream infection with secondary meningeal involvement 
and therefore advises the use of large doses of anti-meningococcus 
serum intravenously as soon as the diagnosis is made in addition to 



intrathecal injections. The results so far obtained seem to be better 
than when intraspinal injections alone are used. Frich also recom- 
mends that all patients with positive signs and symptoms be given both 
intraspinal and intravenous injections of serum. Large doses of serum, 
both intravenously and intraspinally at frequent intervals apparently 
do no harm, lower the mortality, prevent serious complications and 
shorten the period of convalescence. 

Anti-pneumococcus Serum. Washburn, Mennes, Pane and numer- 
ous other early investigators attempted to produce anti-pneumococcus 
sera for the treatment of man, but their results were irregular and not 
encouraging. An important advance in the production of anti-pneumo- 
coccus serum was made when Neufeld and Handel in 1909 pointed out 
that pneumococci can be divided into various immunological groups, 
and that no curative properties can be expected from a given serum 
unless it is homologous for the type that causes the infection. This 
work has been confirmed and extended by Dochez and Gillespie, Cole, 
Lister and many others. At present we recognize four groups. Groups 
I and II are immunologically distinct groups, Group III is that of 
the streptococcus or pneumococcus mucosus, and Group IV a heter- 
ogeneous group of pneumococci which cannot be classified under the 
other three groups. The following table, taken from Park (" The 
Practical Application of Serum Therapy," Transactions of the Con- 
gress of American Physicians and Surgeons, 1916, x, 118) gives the 
group-incidence and mortality : 



Per cent, inci- 

Per cent, mor-? 

University of Penna. 
Hospital, Richardson 








Per cent, 

Per cent, 

I. . 























Other bacteria .... 

* Presbyterian Hospital, Longcope. 

From this table it appears that about 30 per cent, of the cases of pneu- 
monia and about one-third of the total deaths from the disease are 
caused by Type I pneumococci. In the United States Cole claims that 
75 per cent, of all pneumonia cases are caused by Types I, II and III, and 
25 per cent, by Type IV. Lister, in South Africa, finds Type IV very 
common among the negroes in the Rand. So far only Type I and 
Type II sera have given encouraging results. The antigenic value of 
Type III pneumococcus is exceedingly low, and that of Type IV vari- 
able. From the more recent work of Raphael it would appear that 
sera produced against various strains of pneumococci are in a sense 
strictly monovalent and also that only virulent pneumococci are suf- 
ficiently antigenic to produce antisera of distinct value. 

The sera against infection with Type I organisms have been used 
extensively and appear to have given especially good results. The 


Type II antiserum, however, is much less efficacious and thus far its 
therapeutic value is questionable. The Types III and IV antisera 
have no clinical value. Dochez reports sixty-five cases treated with 
Type I serum, with a mortality of 6.6 per cent., as compared with a 
mortality of 25 per cent, in Type I cases not treated with serum. 
Type II cases treated with serum have a mortality of 25 per cent, 
as compared with 61 per cent, without the use of specific sera. When 
patients are treated early, they do well, and large doses of serum 
should be given as soon as the type of infection has been determined. 
Cole advises an intravenous injection of 80 to 100 c.c. of serum diluted 
with an equal amount of salt solution and repeated every twelve hours 
until improvement occurs. The average total amount of serum required 
in the Hospital of the Rockefeller Institute was about 250 c.c. The 
injection of such large doses of serum is not entirely without possible 
harm to the patient because of reaction to the foreign protein. The 
possibility of severe serum .sickness should further be taken into con- 
sideration. From evidence recently collected, more particularly in the 
United States Army, the value of anti-pneumococcus sera has been 
questioned. Parallel series of cases showed no important difference 
in mortality between series receiving anti-pneumococcus serum, normal 
horse serum or no serum whatever. The patients were young men who 
had passed rigid physical examinations and therefore were good risks 
in acute infections. It does not follow that other classes of patients 
would show the same results. There is also great variation in the mor- 
tality of different epidemics, and also normally in different ages, so 
that only a sufficiently large number of treated cases extensively con- 
trolled will form a trustworthy basis of actual comparison as to the 
death rate, which is, after all, the final criterion as to the actual value 
of the serum. Cecil and Blake have recently examined the question 
on the basis of experiments with monkeys. They find that the admin- 
istration of normal horse serum has no beneficial effect on experimental 
pneumococcus Type I pneumonia but that the intravenous administra- 
tion of specific Type I antiserum, particularly if given early and fre- 
quently, " exercises a specific therapeutic effect, frees the blood 
promptly and permanently from pneumococci, shortens the course of 
the disease and greatly moderates its severity." The treatment of 
lobar pneumonia with Cole's serum at present is best carried out in 
institutions where it is possible to make accurate bacteriological diag- 
nosis and differentiation of the types of the cocci, and where intra- 
venous administration of large doses of sera can be accomplished with 
the largest margin of safety to the patient. 

Kyes has carried out extensive investigations on the clinical value of 
a serum produced by injecting massive doses of virulent pneumococci 
into the domestic fowl. The reason for the selection of the fowl as 
supply animal is that no matter how virulent pneumococci are for other 
species, they do not occasion disease in fowls, and therefore large doses 
can be injected with impunity. The initial dose in most instances is a 
surface growth equal to that of 240 test-tube slants. The average 


subsequent doses are approximately 400 test-tube slants each. All the 
injections are made intraperitoneally. Injections are given every two 
weeks over periods of from four months to two years. One week after 
the sixth injection a trial bleeding is made and thereafter at intervals of 
two weeks, alternating with the biweekly injections. The sera possess 
a high content of agglutinins and bacteriolysins and also exhibit a 
marked therapeutic influence upon infected animals. Clinically the 
serum is used in doses of 2.5 c.c., and injections made slowly. A ma- 
jority of the cases have received one injection daily, but not infre- 
quently two injections are given the same day. The injections are 
continued until the temperature remains below 100 F. Of 538 cases 
not treated, 244 cases died, the death rate being 45.3 per cent. Of the 
175 similar cases treated with serum the death rate was 20.8 per cent. 
In the ward in which the serum was employed the death rate during 
the six weeks prior to the introduction of the serum treatment was 55 
per cent. During the six weeks subsequent to the withdrawal of the 
serum treatment, the death rate was 51 per cent. These results are 
distinctly encouraging. McClelland has recently reported the results 
in 322 cases of lobar pneumonia in soldiers at Camp Grant in which 
treatment with fowl serum was given and concludes that the low 
mortality (7.7 per cent.) together with the favorable modification of 
clinical symptoms by the serum would seem to indicate the extension 
of its use in pneumococcus pneumonia. Considering the fact that 
these cases were in selected young men of military age, and that the 
author does not give a comparative mortality among non-treated cases, 
much of the value of this paper is lost. The serum has also been used 
by Litchfield with great benefit in a series of pneumococcus meningitis 
cases. Gray employed the Kyes serum in 234 cases of pneumococcus 
pneumonia with a mortality of 16.8 per cent., whereas in similar cases 
treated in the same way except that they received no serum, the mor- 
tality was 63.6 per cent. Much laboratory and clinical work remains to 
be done before any definite conclusive evidence as to the value of 
polyvalent or antigroup sera can be drawn with any degree of safety. 
Pneumococcus sera act in part by opsonization of the cocci, thus favor- 
ing phagocytosis. The standardization requirements of the Hygiene 
Laboratory, Washington, call for a serum that shall protect white mice 
against Type I pneumococcus only. It is felt by Ferry and Blanchard 
and many others that a potent polyvalent serum is an absolute necessity. 
These authors recently succeeded in immunizing horses with Types I, 
II and III and some strains of Type IV. This serum in doses of 0.2 c.c. 
protected mice against infection of Types I, III and IV organisms (ten 
million M.L.D.). 

Anti-cholera Sera. While antisera against cholera have been pro- 
duced by several investigators, the treatment of the disease with these 
sera has not given the best of results. Metchnikoff, Roux and others 
have prepared sera against the toxins of organisms cultivated in col- 
lodion sacs. McFadyen used ground organisms. Kraus used the toxin 
of the El Tor vibrio as antigen. This organism was obtained by 


Gottschliech in 1905 from the intestinal contents of pilgrims who had 
died at El Tor from dysentery, and is not a true cholera vibrio but 
very closely related to it. Kraus recommended his antitoxin for the 
treatment of the cholera. Schurupoff treated one-and-a half to two- 
day-old cultures of the vibrio with alkali and injected this toxic material 
into horses at six to ten-day intervals. Under Kolle's direction, Car- 
riere and Tomarkin injected horses and goats with cholera cultures con- 
taining also the toxic derivatives and used the mixed sera of these 
animals. They found that these sera are more valuable against cholera 
peritonitis of guinea-pigs than any other animal. 

Ketscher and Kernig used Kraus' serum in 119 severe and mod- 
erately severe cases with a death rate of 58 per cent, in those who 
received subcutaneous injections, and 50 per cent, when used intrave- 
nously, while among the non-injected cases the mortality was 63.4 per 
cent Others have found among the serum-treated cases a mortality of 
57-5 P 61 " cent, and among the control cases 84.3 per cent. This serum 
was administered by Jegunoff intravenously together with physiological 
salt solution, giving at first 140 c.c. of serum with 500 c.c. to 700 c.c. of 
physiological salt solution and subsequently a second injection of 80 to 
1 20 c.c. of serum within seven and one-half to twenty-three hours after 
the primary injection. During the Russian epidemics in 1908 and 1909 
it was shown that large doses of sera did not harm the patients. It 
was originally believed that large doses of sera lead to quick destruc- 
tion of the vibrios with subsequent intoxication, but this has not proven 
to be the case. During these epidemics Salimbeni's and Kraus' sera 
did not give satisfactory results. Schurupoff's serum was considerably 
better, and the best results were obtained with the serum prepared 
according to Carriere and Tomarkin. This serum was given in doses 
of 50 c.c. to loo c.c. diluted with salt solution subcutaneously and intra- 
venously and resulted in quick improvement. Von Stiihlern and 
Tuschinski treated 149 algid cases with fifty-six deaths; twenty-five 
moderate and thirteen early cases were treated with no deaths. From 
a total of 187 cases the mortality was 29.9 per cent. The serum should 
be applied as early as possible. Cholera antisera contain bacteriolytic, 
agglutinative, probably anti-endotoxic, complement-fixing antibodies, 
and also tropins. Because of the variety of sera used and the incon- 
clusive reports given it is exceedingly difficult to reach a definite con- 
clusion regarding the curative value of anti-cholera sera. It seems to 
us that Carriere and Tomarkin's serum is the most promising. 

The Use of Anti-anthrax Serum. The treatment of anthrax has 
consisted mainly in excision of the pustule, application of chemical or 
thermal cautery, and the injection of germicides as iodine, mercuric 
chlorid or phenol in the regions of the pustule, but all these methods 
are objectional because they are likely to produce scars and disfigure- 
ment. Excision may furthermore increase the danger of systemic 
infection. Sclavo, Deutsch, Sobernheim and others have produced 
immune sera by immunization of the sheep, horse and ass with attenu- 
ated culture of anthrax bacilli. From the work of Marchoux we know 


that this serum possesses prophylactic and therapeutic properties in 
animals. Anti-anthrax serum has been used for several years, espe- 
cially in Italy, France and England, with encouraging results. Sclavo 
treated his cases without excision and in a series of 164 cases treated 
with specific serum this author reduced the mortality from 24 per cent, 
to 5.3 per cent. Sclavo recommends 30 to 40 c.c. serum administered 
subcutaneously in doses of 10 c.c. on the first day and repeated if neces- 
sary on the next day. In severe infections 10 c.c. were given by the 
intravenous route. In severe cases it is advisable to give the injections 
in massive doses of 80 c.c. to 100 c.c. and preferably intravenously. 
Shera advises administration of 20 c.c. every twelve hours until pyrexia 
ceases. Regan recently injected the serum (10 c.c. to 15 c.c.) into the 
tissues surrounding the pustule and found that it possesses none of the 
disadvantages of the previous methods of local treatment, and has a 
very rapid and complete effect on the pustule, not only in arresting its 
further development but also in producing a subsidence of all local 
inflammatory symptoms. He advises also general treatment either 
intramuscularly or intravenously. Local treatment in order to effect 
a cure must anticipate the onset of an anthrax septicemia. In case 
the organisms have been demonstrated in the bloodstream the prog- 
nosis is usually grave. In this case 200 c.c. of serum is not excessive, 
and if necessary should be repeated until a negative blood culture is 
obtained. In intestinal anthrax large doses of serum should be given 
by the intravenous route. Penna and Beltrami and Penna, Cuenca and 
Kraus have obtained good results with normal beef serum. Their mor- 
tality was 6.2 per cent, in 372 cases, while the mortality previous to this 
period of treatment was about 10 per cent. These authors advise the 
use of 30 to 50 c.c. of normal beef serum administered subcutaneously. 
If no improvement occurs the injections should be repeated every 
twelve, twenty-four or thirty-six hours, but it seldom happens that a 
patient requires more than two or three injections. In severe cases 
intravenous administration is recommended. Similar favorable results 
were obtained by Solari and Langon, but Lignieres has reported un- 
favorably upon the curative action of normal beef serum, stating that 
it is inferior to horse anti-anthrax serum. He calls attention to the 
prevalence of anthrax in cattle as evidence of the apparent lack of 
natural resistance to the disease. More recently Kolmer, Wanner and 
Koehler pointed out on the basis of their experiments that normal beef 
serum as secured from animals under ordinary conditions is but feebly 
protective or curative for anthrax and while its administration as 
described by Penna and his associates may favorably influence the pus- 
tule it is doubtful if the serum is sufficiently powerful to influence 
anthrax bacteremia. According to Kolmer, cases with sterile blood 
culture always recover. The potent factor of anti-anthrax serum 
appears to be a thermostable opsonin. 

The Serum Treatment of Plague. The therapeutic value of anti- 
plague serum is still a matter of dispute. Plague epidemics are exceed- 
ingly variable in character. Irregularity in the gravity of the disease 


in different individuals is of common occurrence. A wide variety 
of antisera has been employed, but no attempt has been made to stand- 
ardize the different sera. In many instances the cases treated were 
especially selected and moribund cases excluded. The result is that much 
of the existing statistical data is unreliable. Yersin, Calmette and Borrel 
were the first to show that the serum of an animal immunized to bacillus 
pestis has protective qualities and Yersin is credited with the production 
of anti-plague horse serum. This serum was prepared by immunization 
of horses first with dead and subsequently with living bacilli. Tavell's 
serum was prepared on the same principle, but Hata and also Kraus 
immunized their animals with dead bacilli alone and claim that these 
sera compare favorably with sera produced by the injection of living 
bacilli. The use of dead bacilli minimizes the danger of laboratory in- 
fections. Soon after the discovery of the nucleoproteins by Ferrannini, 
Galeotti and Lustig employed nucleoproteins from plague bacilli as 
antigen for the production of anti-plague serum. For this purpose the 
bacilli were broken down in i per cent. KOH solution and the nucleo- 
proteins precipitated by the addition of acetic acid and then suspended 
in salt solution. Rowland also used a similar antigen, and others have 
employed a variety of extracts as antigens. 

The serum at present most commonly used is obtained from horses 
after repeated intravenous injections of killed cultures sometimes fol- 
lowed by living organisms. Experimentally the sera show considerable 
strength in protecting animals against infection and exhibit specific 
bacteriolytic, bacteriotropic, agglutinative and antitoxic qualities. The 
antitoxic titer is usually very low. According to Kraus, Yersin's serum 
is not any better than the sera prepared with dead bacilli or nucleo- 
proteins. Yersin used his serum in twenty-six cases during the epi- 
demics of 1896 in Canton and Amoy, China, with a mortality of 7.6 
per cent., while the mortality in cases not treated with serum reached 
80 per cent, to 90 per cent. In 1897 141 cases were treated in Bombay 
and Cutch-Mandir with a mortality of 49 per cent. Of 685 cases not 
treated 80 per cent. died. In 1898 thirty-three cases were treated in 
Anam with Yersin's serum. The death rate among non-treated cases 
was 100 per cent, but was 42 per cent, among the serum-treated cases. 
It was found that the serum was entirely inefficient in cases with the 
pneumonic form of the disease. The German Commission at Bombay 
claimed that the low mortality (50 per cent.) of serum-treated cases was 
due to the selection of mild cases or cases arriving at the hospitals 
during the first or second day of their illness. Clemon also failed to 
obtain results in his fifty cases in which he injected as much as 60 c.c. 
of the Yersin serum. The Indian Plague Commission did not report 
favorably on Yersin's serum. Calmette and Salimbeni obtained very 
good results with serotherapy in Oporto, Portugal ; of 142 treated cases 
twenty-one died, while of seventy-two not treated forty-six died. Kos- 
sel and Frosch and others studied this epidemic and found it to be of 
a mild type. During the Manchurian campaign serum treatments 
were entirely inefficient. Choksy injected large doses (100 c.c) 


of the Parisian serum in his cases, repeating this six to eight 
hours later, and if necessary followed again by another injec- 
tion. The next two days he administered 20 to 50 c.c., so that 
an adult received a total of 590 c.c. From a careful study he obtained 
a mortality of 72.5 per cent, among the serum-treated cases, and 82.3 
per cent, among his control cases. This author also emphasizes the 
enormous advantage of early injections. In a series of 222 cases 
treated on the second, third, fourth, fifth, sixth and seventh day of 
illness he found the mortality as follows: 38.2, 56.7, 58.2, 50.8, 62.9, 
60.0, and 75 per cent, respectively. According to Burnet, satisfactory 
results have been obtained in Queensland at the Colmolie Plague Hos- 
pital. Among 190 serum-treated cases during the period 1901 to 1907 
the mortality was 29.7 per cent., while the mortality during the same 
period among non-treated cases was 73.9. Penna in Argentina injects 
massive doses 80 to 100 c.c. intravenously, and repeats the injection of 
50 c.c. after twelve to twenty-four hours. Among 664 treated cases 
during the period 1905 to 1912 he reported a mortality as high as 23 
per cent, in 1906, and a mortality of 7.3 per cent, in 1912, the average 
mortality was 12.5 per cent. From 1914 to the middle of 1919 Kraus' 
serum was used with an average mortality of 7.8 per cent. Kraus' 
serum, therefore, gave better results than Yersin's serum. Intravenous 
or intramuscular injections can be employed to ensure rapid absorption 
and the injections should be continued every twelve to twenty-four hours 
for two or more days until diarrhea has been controlled and the disease 
begins to subside. From all these studies we may conclude that although 
serum therapy of plague has not given striking results as diphtheria 
antitoxin in diphtheria, still it is the only specific means of combat- 
ing the disease and when given early and in massive doses appar- 
ently influences the disease favorably. 

Anti-bacterial Serum in the Treatment of Diphtheria Carriers. 
Although Wassermann in 1902 recommended the use of a bactericidal 
serum, Martin was the first to use anti-bacterial serum in the treatment 
of diphtheria carriers. Martin injected diphtheria bacilli intravenously 
or intraperitoneally into horses and obtained sera with marked agglu- 
tinating properties. He claims that this serum has, when applied 
locally, the property of causing a rapid decrease in number of living 
bacilli in the throat. The best results were obtained by incorporating 
the dried serum with gum and using it in the form of pastilles. Dopter 
and many others have reported a decrease in the carrier period by the 
use of anti-bacterial serum. More recently Roskam and Arloing and 
Stevenin have called attention to the value of this method of treatment. 
Ecker immunized sheep with various strains of diphtheria bacilli, and 
by using massive doses obtained a potent agglutinative and lytic serum. 
To this serum fresh guinea-pig complement was added and the mixture 
sprayed by means of atomizers into the nasal passages, and over tonsils, 
fauces and pharynx four and five times a day. A total of forty-eight cases 
were treated, eighteen convalescent and thirty contact carriers. The 
duration of the carrier state after the introduction of the serum was seven 


days, while the average duration of eighty-seven control cases was 18.6 
days. A few cases proved to be persistent carriers. The less favorable 
results obtained by Kretschmer, Blumenau and Nolf may be explained 
by their small series of treated cases, weak sera and ineffective methods 
of application of the serum. Although the results so far obtained are 
not entirely convincing, the use of anti-bacterial serum in the treatment 
of diphtheria still deserves careful consideration. It is not pos- 
sible to resort to tonsillectomy or adenoidectomy in all instances, 
and the majority of antiseptics are irritant. In many instances it is 
practically impossible to reach the organisms because they are buried 
in crypts, and tonsillectomy remains as the favored mode of treatment, 
although even this method is not invariably successful. 

Anti-gonococcus Sera. The early work of Rogers and Torrey 
has led to attempts at treatment of gonococcal infections by means of 
immune sera. Torrey's serum is prepared by injecting sheep with 
dead and subsequently living cultures of virulent strains of the gono- 
coccus. Although efforts have been made to treat urethral, vulvar 
and vaginal gonorrhea by local applications of serum the disposition 
of the organisms in deep glands has been sufficient to result in the 
failure of this method. Recent studies of Debre and Paraf offer some 
encouragement for the treatment of gonorrheal rheumatism by the use 
of polyvalent sera, but they find that local injections about the site 
of the disease are more effective than general subcutaneous or intra- 
venous injections. Further studies may demonstrate the value of 
serum treatment of chronic gonorrheal infections, but at the present 
time the method cannot be highly recommended. 

Serum Treatment of Tuberculosis. The best-known sera for use 
in tuberculosis are those of Maragliano and Marmorek. The first is 
prepared by immunizing horses with a mixture of a toxic filtrate of 
the bacilli and an aqueous extract of killed virulent tubercle bacilli. 
One cubic centimetre of the immune horse serum is injected into the 
patient every other day for a period of one and one-half months. A 
number of Italian workers found the serum effective, but other ob- 
servers have not been convinced of its value. Marmorek's serum is 
prepared by inoculating horses with young tubercle bacilli poor in acid 
fast character. In addition, Marmorek immunized animals with pure 
cultures of streptococci obtained from the sputum of tuberculous 
patients. This serum is injected subcutaneously in daily doses of from 
5 to 10 c.c. or intrarectally in doses of from 10 to 20 c.c. A number of 
workers, as for instance Wohlberg, have reported a favorable influence ; 
others deny this effect. Wohlberg found the best results in scrofulous 
cases but not in cases of fully developed tuberculosis. The benefits of 
serum therapy of tuberculosis have not been convincing. 

Serum Treatment of Typhoid Fever. Lewin and Yes, Beumer 
and Pfeiffer and Chantemesse were among the first to produce antisera 
for this disease. Chantemesse's antiserum was prepared by immuniz- 
ing horses with soluble toxins of the typhoid bacillus. Balthasard 
tested this serum and found it to agglutinate typhoid bacilli in very 


high dilutions and to protect animals under experimental conditions. 
In 1000 cases of typhoid fever, Chantemesse reduced the mortality to 
4.3 per cent, whereas the mortality among 5621 cases at the other 
hospitals in Paris not treated with serum was 17 per cent. Similar 
favorable reports were made by Brunon and Josias. Kraus and 
Stenitzer also produced antitoxic sera by immunizing their animals 
with soluble toxins and Cjaupp claims that the serum can be used with 
advantage in the treatment of the disease. Besredka and Liidke pre- 
pared sera by immunizing horses and goats with the endotoxin of the 
typhoid bacillus, but it seems that the serum is not primarily an anti- 
endotoxin but rather a bactericidal serum which neutralizes both the 
exo- and endotoxins of the typhoid bacillus. According to Andriesen 
and Cinca, it can be used clinically. Sera were also prepared by im- 
munizing animals with sensitized cultures of the typhoid bacillus and 
also with products obtained by digesting typhoid bacilli with trypsin. 
This toxic compound is known as "Fermotoxin" (Gottstein and 
Mathes). Rommel and Herman failed to obtain encouraging results 
with serum prepared by immunization with sensitized bacilli. The most 
favorable results, however, were secured by Rodet and Langrifoul. 
These authors immunized horses intravenously with both living cultures 
and old endotoxins, and in a summary of 400 cases Rodet finds that by 
repeated injections of this serum in doses from 10 to 20 c.c. given sub- 
cutaneously every other day the duration of the fever is markedly 
reduced in cases that are treated early. Serum treatment appears to 
reduce the bacteremia. It is also known that twenty-four hours after 
the injection of serum a definite increase in splenic dullness is observed, 
which presumably indicates a general stimulation of the lymphoid and 
myeloid tissue. The self -limitation of the disease, in the absence of 
complications, throws some doubt on the practical value of such sera. 


The use of the patient's own serum in the treatment of his disease 
has been suggested and applied by a number of workers. Gilbert, 
Marcon and many others treated tuberculous peritonitis and tubercu- 
lous pleurisy with effusion, by the subcutaneous injection of i. c.c. to 
2. c.c. of the patient's own serum and claim that the absorption of the 
exudate is greatly increased and an immediate improvement occurs. 
Eisner observed a leucocytosis following the injection of the serum 
in experimental tuberculous infections of rabbits and guinea-pigs and 
believes that this fact explains the favorable results reported in this 
method of treatment. Other investigators believe that specific antibodies 
favorably influence the process, but Levy, Valenzi and others are 
inclined to believe that the results are independent of the injections. 
It is possible that simultaneously with the transfer of the serum a 
minute amount of tuberculin is introduced. The exact nature of the 
phenomenon is, however, obscure. In influenza, Malta fever and 
typhoid fever Modinos has also obtained beneficial effects and Jez 
applied the treatment favorably in erysipelas. Capogrossi more re- 


cently treated two cases of cerebrospinal meningitis with fairly good 
results. Hodenpyl treated a case of carcinoma with the patient's own 
ascitic fluid with apparent success. He used this fluid in large quanti- 
ties in a number of cases but only with transient success. Risley also 
applied this method of treatment in sixty-five cases of cancer, using 
ascitic fluid from cancer cases and also other body fluids from non- 
cancerous cases. N'o encouragement for this method has been found 
in experimentally inoculated mouse cancers and the subsequent history 
of Hodenpyl's cases showed no permanent improvement. Auto-serum 
therapy has further been applied in obstinate and chronic skin troubles, 
such as psoriasis, dermatitis herpetiformis, pemphigus, lichen ruber, 
lichen planus, urticaria and squamous eczema. The serum is used in 
doses of 30 to 40 c.c. and repeated from two to six times at intervals 
of from three to five days. 

Auto-serum Therapy in Syphilis. Perhaps the most widely 
used auto-serum therapy is the salvarsanized auto-serum in the 
treatment of parasyphilis. The treatment of syphilis of the ner- 
vous system with salvarsan or neosalvarsan alone has not given 
the results expected. This is because the choroid plexus filters 
out these compounds, preventing their entry into the cerebrospinal 
fluid. It has been shown by Plaut that the serum of patients who have 
received salvarsan possesses antisyphilitic power, while normal serum 
fails to display this characteristic. Similarly Meirowsky and Hart- 
mann and Gibbs and Calthrop obtained good results in the subcutaneous 
treatment of lues with serum of salvarsanized patients. According to 
Swift and Ellis, salvarsanized serum inhibits the treponema more in- 
tensively if heated to 56 C. for half an hour. These facts formed the 
underlying principles for the treatment of late syphilis with salvarsan- 
ized serum. Swift and Ellis injected salvarsanized serum intrathecally 
in a number of cases of tabes dorsalis and in other manifestations of 
neurosyphilis, and reported most encouraging results in both clinical 
and immunological manifestations. This work has since been confirmed 
by a large number of authors. The treatment is of special value in the 
earlier stages of neurosyphilis. Unfavorable results have been ob- 
served, as for instance the spasmodic retention of urine. As a result 
of long standing of the salvarsanized serum prior to its use, the drug 
may become oxidized with a marked increase in toxicity. 

Method of Treatment. Six-tenths to nine-tenths gram of salvar- 
san or neosalvarsan is injected intravenously. One hour later 40 c.c. of 
the patient's blood is withdrawn, allowed to coagulate and centrifuged. 
Twelve cubic centimetres of the sterile serum is diluted with 18 c.c. of 
sterile physiological salt solution to make it a 40 per cent, dilution and 
heated for half an hour at 56 C. A lumbar puncture is then per- 
formed, and 25 to 30 c.c. of fluid is withdrawn, and the serum very 
slowly injected. Swift and Ellis recommend the gravitation method of 
injection to prevent a sudden increase in intrathecal pressure. The 
patient is then kept in bed for twenty-four hours and the foot of the 
bed elevated for part of this time. The reaction is usually of a mild 


type, including slight fever, pain in the legs, but in rare instances violent 
symptoms have been observed. Before and after the treatment a Was- 
permann test, the globulin test and a cell count should be made. After 
one week or more the treatment can be safely repeated until definite 
improvement occurs. 


Weisbecker in 1897 appeared to be the first to have used blood 
serum of convalescents, in cases of scarlet fever, but with little success. 
Huber and Blumenthal, von Leyden and others renewed the interest 
in convalescent serum therapy but failed to reach any definite con- 
clusion probably because of the small doses employed. Reiss and 
Jungmann, Koch, Zingher and Weaver more recently applied the 
treatment with a fair degree of success. Reiss and Jungmann gave 
intravenous injections of 40 c.c. to 100 c.c. and drew the blood from 
scarlet-fever convalescents about the end of the third or beginning of the 
fourth week of the disease, testing each serum for the possibility of 
syphilis and for sterility. Zingher injected citrated whole blood intra- 
muscularly in doses of 120 c.c. to 240 c.c. and repeated in two or three 
days if necessary. Weaver drew the blood from convalescents between 
the twentieth to twenty-eighth day, only such convalescents being selected 
who had not been septic and who gave a negative Wassermann reaction. 
The sera were tested for sterility and used pooled. Intramuscular in- 
jections were given in doses of 25 c.c. to 90 c.c., 60 c.c. being the usual 
amount. The effects of the serum are rapid and start with a sudden drop 
in temperature and general improvement of the patient within twenty- 
four hours after the administration of the serum. The best results 
are obtained when the patients are treated early in the disease. Kling 
and Widfeldt also reported favorable results in their series of cases 
during an epidemic of 237 cases at Stockholm in 1918. This method has 
not been widely adopted and there is still much question as to whether 
improvement is due to the treatment or to the natural self -limitation 
of the disease. 

Monvoisin has recently reported encouraging results in typhus fever 
by intravenous injections of human convalescent serum. One or two 
cubic centimetres of serum brought a marked drop in temperature and 
general improvement in the patient. Monvoisin noted a decrease in 
mortality from 30 down to 10.34 per cent, by the use of convalescent 
sera. The serum was obtained from a patient on the eighth day after 
subsidence of fever. Favorable results were also reported by Teissier 
in cases of severe and hemorrhagic smallpox. In leprosy the serum 
obtained from cantharides blisters on lepers has been reported to 
be of value. 

Bleyer recently injected immune human blood into a series of forty- 
five cases of whooping-cough in the early weeks of the disease. This 
series was divided into three groups. The first group received blood 
from persons who were convalescent or who had recovered from 
whooping-cough within three months. In the second series the blood 


was from persons who had the disease at more remote periods, and the 
third group from persons who, so far as they knew, had never suffered 
with whooping-cough. The stage at which the treatment was given 
was about the same in the three groups and the dosage depended upon 
the body weight of the patient, varying between 40 c.c. and 125 c.c., 
divided into two, three or four doses and injected into the gluteus 
muscles. In the first group there were no deaths and no complications, 
and the course of the disease was in no definite way different from 
the usual course. The second group showed quite as satisfactory im- 
provement as in the first group. In the third group there were two 
pneumonia cases with one death and one case which apparently was 
favorably influenced by normal serum treatment. The groups are so small 
and the difference so slight as to give no reason for regarding this 
mode of treatment as particularly effective. Vaccine treatment of this 
disease gives much greater promise of success. 

During the recent great epidemics of so-called influenza, conva- 
lescent serum was used irt a considerable number of cases which 
developed pneumonia. In many instances there was marked improve- 
ment, but there is no clear indication that the results were specific or 
that they depended absolutely upon the serum treatment. 


Introduction. The preparation of the immune sera discussed above 
depends not only upon knowledge of the etiological agent of the disease 
concerned but also necessitates the isolation of the organism in pure 
culture. Several infectious agents are known to exist in blood and 
tissues, since the diseases may be transmitted by means of inoculation 
of blood, organs or organ extracts. Many of these agents are so small 
as to pass through porcelain filters and are spoken of as the filterable 
viruses. Some of these viruses have been observed to contain minute 
globoid bodies which have been obtained in pure culture, but under 
such conditions that they have not served well as antigens for the 
production of immune sera. If immunization be attempted by injec- 
tions of the blood or tissues containing the infective agents, the result- 
ing immune serum contains not only antibodies for the infective agent 
but also for the tissues. If these tissues happen to be from the same 
species into which the serum is to be injected the hemagglutinins, 
hemolysins and cytolysins in the immune serum may seriously damage 
or even kill the individual so treated. Active immunization by the use 
of infected tissues appears to progress favorably in spite of the presence 
of the tissues, as seen in the active immunization of man and other 
animals by the use of the virus of rabies* contained in the dried spinal 
cords of rabbits. It is in the production of sera for passive immuniza- 
tion that the danger from simultaneously formed tissue antibodies ap- 
pears. Rous, Robertson and Oliver have studied this problem with a 
view to removing from the immune serum these harmful elements. 
After the immune serum is prepared the tissue antibodies are removed 
by selective absorption with red blood-corpuscles, since these cells re- 


move the most important source of danger, the hemagglutinins and the 
hemolysins; undoubtedly many of the other tissue antibodies, as the 
cytolysins, are reduced in amount. For example, they immunized a 
goat with megatheriolysin and finely-ground liver, spleen and kidney, 
as well as defibrinated blood, of guinea-pigs. The immune serum was 
then repeatedly mixed with guinea-pig blood-cells until all the hemag- 
glutinin and hemolysin had been removed. The process did not reduce 
the titer of the special antilysin against megatheriolysin either in test 
tube or animal experiments. Guinea-pigs were protected against 
megatheriolysin by the use of this serum and the treatment of the 
serum by selective absorption removed practically all the elements dan- 
gerous for the guinea-pig. Similar experiments were performed using 
as antigen the blood of rabbits suffering from pneumococcus 
septicemia. It was found that absorption, by means of blood, of 
anti-poliomyelitis serum produced no change in its protective value. 
Experiments were also performed with the Rous chicken sarcoma, a 
tumor caused by a filterable virus. The immune serum was prepared 
by injecting into geese a mixture of tumor tissue and the blood of 
moribund fowl since under these circumstances the blood contains the 
causative agent. The immune serum was treated with fowl blood- 
corpuscles to remove the tissue antibodies. The serum so treated, when 
employed in proper ratio to the amount of tumor inoculated, served 
to protect fowl against the subsequent growth and development of the 
tumor, whereas growth proceeded regularly in the unprotected con- 
trols. Rous makes no claim as to high protective value but that some 
such power is developed is undoubted. 

The work quoted above is of the utmost importance in establishing 
the important principles that must be observed in the preparation of 
immune sera against infective agents either known or unknown when 
used as antigens in animal tissues. The studies are recent and have not 
as yet been widely applied. The immune sera against infections of 
undetermined cause to be described in this section were studied before 
the work of Rous and his associates appeared, and it is probable that 
the methods of preparation may be considerably modified in the course 
of time. The inclusion of acute anterior poliomyelitis in this group 
is justified only on the ground of dissension as to whether the disease 
is due to the globoid bodies described by Flexner and his collaborators 
or to the pleomorphic streptococcus studied by Rosenow, Nuzum 
and others. 

Anti-poliomyelitis Serum. That one attack of poliomyelitis pro- 
tects against subsequent infection has been known for many years. 
Levaditi and Landsteiner and also Flexner and Lewis in 1910 
demonstrated that the serum of convalescents and of monkeys recov- 
ered from the disease protects against infection. Treatment of human 
cases of the disease was applied by Netter in 1916. This author 
injected intrathecally the serum of recovered patients in doses of 5 to 
13 c.c. for a period of eight days with most encouraging results. He 
believed that the best serum is found in individuals whose acute attack 


dates back from three months to four years. Flexner carried out 
experiments with monkeys and proved that the serum of recovered 
cases was efficacious in the cure of these animals. In 1916-1917 this 
author used the serum extensively during the epidemic in New York 
and recommends the combination of intraspinal and intravenous in- 
jections. Children were given combined doses of 5 to 10 c.c. intra- 
spinally and 30 to 40 c.c. intravenously. The possibility of conveying 
the disease is not considered a danger, because the virus has never been 
detected in the blood. The only difficulty encountered in this method 
of treatment is that of securing sufficient quantities of serum. Pooling 
of sera is of the greatest advantage, since the antibody content may 
vary widely in the sera of different persons. 

During the epidemic of 1917 Mathers, Rosenow, Towne and 
Wheeler, Nuzum and Herzog, and later Nuzum reported the discovery 
of a pleomorphic streptococcus which they had constantly observed in 
the brain and spinal cord, and also in the cerebrospinal fluid in human 
cases of poliomyelitis. Flexner and Noguchi, Smillie and many others 
deny the etiological importance of this streptococcus. Rosenow, Nuzum 
and Willy claim to have produced sera with definite protective and cura- 
tive effects. In the hands of Nuzum and Willy serum treatment re- 
duced the mortality in a series of 159 cases from 38 per cent, to 
11.9 per cent. 

Amoss reported that only imperfect success in developing antibodies 
in rabbits and monkeys has attended the repeated injection of cultures 
of the globoid bodies of Flexner and Noguchi and also failed to find 
evidence that Rosenow's serum is either therapeutically effective in 
monkeys or possesses antibodies of the same nature as those present in 
the blood of monkeys which have recovered from experimental polio- 
myelitis. Since the antibodies in convalescent poliomyelitis serum in man 
and monkey are identical, this author states that any antibodies present 
in Rosenow's horse serum do not conform to those occurring in human 
convalescent serum. Again Amoss and Eberson in a later paper con- 
cluded that the anti-streptococcus serum of Nuzum and Willy fails to 
show in the monkey neutralizing or therapeutic power against small 
doses of the virus of poliomyelitis. Under the same conditions the 
serum of monkeys which had recovered from experimental poliomye- 
litis proved neutralizing and protective. These facts leave some doubt 
as to the actual value of anti-poliomyelitis horse serum, and until 
more conclusive evidence has been brought forward by the supporters 
of the streptococcus as an etiological factor we believe that the only 
effective serum existing is that of convalescent or recovered cases. 
Neustadter and Banzhaf immunized horses against a filtrate obtained 
from the digested brain and cord of a human case of the disease. The 
immune serum gave encouraging results in a few experiments with 
monkeys, but as yet data are too limited to justify a conclusion as to 
the usefulness of this serum. 

Rinderpest. Kolle and Turner injected gradually increasing doses 
of virulent rinderpest blood and also bile of infected animals into oxen 


and obtained potent sera against the rinderpest virus. Of 3318 animals 
treated with this serum 455 or 13.9 per cent, died, while the mortality 
among non-treated animals averages between 85 per cent, and 95 per 
cent. The serum can be used prophylactically in doses of 100 to 200 
c.c. If the virus is simultaneously injected in small doses as advised 
by these authors, the results appear to be extremely satisfactory. 
The serum for curative purposes should be employed within thirty days 
after the onset of fever. 

Anti-hog-cholera Serum. Immunization against hog cholera has 
an important historical as well as a practical bearing since it was in this 
disease that the first attempt to immunize with bacterial products was 
made. Salmon and Theobald Smith published in 1884 their account 
of the production of immune sera in the pigeon by the inoculation of 
killed broth culture of the bacillus of hog cholera. Subsequent studies 
have made it appear that the disease is not due to the bacillus of hog 
cholera and much evidence is at hand to support the view that the 
etiological agent is a filterable virus. At the present time immunity is 
produced in healthy hogs by the injection of blood obtained from 
infected hog's, thus implanting the virus. It is necessary to protect 
the animals employed by passive immunization with a previously- 
prepared antiserum. The animals selected are injected subcutaneously 
with 40 c.c. of anti-hog-cholera serum per hundred pounds of weight. 
Two to three days later the animals receive intravenously 3 or 4 c.c. 
of defibrinated blood obtained from an animal suffering from the 
disease, or the animals may be exposed in infected pens. If the animals 
survive, after a period of one month they are given 5 c.c. of the living 
virus. This is repeated after two or three weeks. The immunized 
animals are bled from the tail. Five cubic centimeters of blood per 
pound of weight are usually withdrawn. The protective power of the 
serum thus obtained is then determined in a series of hogs. For 
prophylactic purposes the* animals receive 40 c.c. subcutaneously per 
hundred pounds of weight or simultaneous injections of virus and 
serum, but this combination is not without danger. For therapeutic 
purposes several injections are necessary and the serum should be 
administered as early as possible. 


Normal serum therapy in man has included the use of both human 
and animal sera. In the treatment of natural or experimental disease 
in man or animals the normal serum employed may be homologous or 
heterologous. The basis of such method of treatment has often been 
entirely empirical, but as serum therapy has been more carefully 
studied the employment of normal serum may be placed in two cate- 
gories, namely that of the non-specific protein treatment of disease 
or that of providing the blood with certain elements necessary for the 
process of clotting. It is to be conceded that a normal serum may be 
employed because of some natural antibodies which it may contain, 
but such a form of passive immunization is much improved if the 


natural antibodies are increased by specific immunization. The use of 
normal serum in non-specific therapy probably increases those non- 
specific factors of defense such as fever, serum enzymes, etc., that 
have already been discussed. In hemophilia, purpura hemorrhagica, 
melena neonatorum and similar hemorrhagic diseases there is a disturb- 
ance of proper balance of those constituents of the blood and tissues 
which provide for coagulation of the blood. Hypotheses differ as to 
the exact mechanism of the process of coagulation, but fundamentally 
it seems necessary to have an equilibrium of prothrombin and anti- 
thrombin. This balance may be upset by an excess of antithrombin, 
by a deficiency in prothrombin, fibrinogen, calcium salts or other ele- 
ments. The interaction of prothrombin, thrombokinase (or thrombo- 
plastin) and calcium salts results in the formation of thrombin. 
Thrombin and fibrinogen interact to form fibrin, the essential element 
of a clot. Blood serum is rich in prothrombin and if a hemorrhagic 
disease be due to prothrombin deficiency, serum treatment is likely to 
be beneficial. If, on the other hand, the disease be due to an excess 
of antithrombin the introduction of prothrombin has little value. 
Similarly hemorrhagic disease with low fibrinogen content is not bene- 
fited by serum treatment. Whipple has found decrease of fibrinogen 
in advanced cirrhosis of the liver with hemorrhage, excess of antithrom- 
bin in aplastic anemia and leucemia and deficiency of prothrombin 
in melena neonatorum. Duke holds that the lack of prothrombin 
is due to a deficiency in the number of platelets, whereas Minot 
and Lee believe that in hemophilia, at least, the slow clotting is due 
to a hereditary defect in the platelets which renders them less avail- 
able for the process of coagulation. Various studies have given different 
results as to the changes found in the elements concerned in clotting. 
Whipple points out that if the phenomenon is studied in the individual 
case rational therapy may be applied. In melena neonatorum the ad- 
ministration of blood serum often gives brilliant results. In other 
hemorrhagic diseases the results are somewhat more variable. If 
hemorrhage has been severe and anemia is marked, the double purpose 
of favoring clotting and replacing lost blood may be served by trans- 
fusion from a suitable and properly-tested donor. The more direct 
the transfusion the less likelihood is there of alteration of the blood 
due to beginning clotting and the greater is the probability of con- 
tributing substances to replace or augment those which may be deficient 
in the patient's blood. 











Introduction. In contrast to the methods of passive immunization, 
i.e., the parenteral introduction of immune sera, vaccine treatment aims 
to increase the resistance to disease by the injection of the causal 
organisms or their products. The duration of this increased resistance 
varies in time according to species and types of organisms injected and 
the individual characterisics of the subject. For instance, vaccination 


against smallpox immunization may last for a considerable number of 
years, while with other organisms, such as the staphylococcus or pneu- 
mococcus the immunity is of relatively short duration. 

The aims of vaccination are either to cause prophylactic resistance 
against disease or to increase an already established resistance. Proph- 
ylactic vaccination against typhoid is an example of the former, while 
the vaccine treatment of furunculosis or gonorrhea are examples 
of the latter. 

The term vaccine is derived from vaccinia or cowpox, and the method 
of protective immunization against smallpox with vaccinia virus was 
called by Jenner " vaccination." This great empirical work was placed 
on a sound scientific basis by Pasteur after he had discovered the 
method of protective inoculation against chicken cholera, and Pasteur 
used the term, vaccination for such inoculations. To-day the simple 
term vaccine is loosely applied and should be restricted to cowpox 
vaccine. Suspensions of bacteria such as typhoid bacilli or pyogenic 
cocci should be designated bacterial vaccines. Wright defines a bac- 
terial vaccine as follows : " Bacterial vaccines are sterilized and enumer- 
ated suspensions of bacteria which furnish, when they dissolve in the 
body, substances which stimulate the healthy tissues to the production 
of specific bacteriotropic substances (or antibodies) which fasten 
upon and directly or indirectly contribute to the destruction of the 
corresponding bacteria." 

Perhaps the first serious attempt to apply practically a bacterial 
vaccine in the treatment of human disease was that of Koch, who in 
1890 employed tuberculin in the treatment of tuberculosis. In 1893 
Frankel treated thirty-seven cases of typhoid fever with subcutaneous 
injections of killed typhoid bacilli. He reported that the course of 
the disease was favorably modified and in a few instances terminated 
by rapid lysis. Rumpf treated a series of cases of typhoid fever with 
bacillus pyocyaneus and obtained equally favorable results, thus throw- 
ing doubt upon the specific character of the treatment and leading into 
the newer field of non-specific therapy. Wright and Douglas soon 
after the discovery of opsonins demonstrated their method of treatment 
by bacterial vaccines under the guidance of the opsonic index. Wright 
stated that a patient who had become infected by an organism such as 
the staphylococcus aureus or the tubercle bacillus would be found to 
have a lowered resistance against these organisms; that this degree 
of want of resistance could be accurately determined, and that the 
resistance could be stimulated and controlled by measured doses of 
a vaccine of the causative organism. Wright's method of treatment 
was based on the principle of strict specificity. It was soon pointed out 
that opsonins are only one link in the defensive chain of the host, and 
the use of the method has been somewhat restricted. The measure of 
opsonins in a given instance was subsequently found not to be a measure 
of the existing degree of total immunity. In the majority of diseases, 
therapeutic vaccination has not withstood the test of time. Wright 
himself, after experiences in the World War, stated that it has been 


accepted that the inoculation of microbes into the already infected 
system is as illogical as to instil further poison into an already poisoned 
body. However, a wide field for prophylactic vaccination is still open. 
Soon after Wright's work bacterial vaccines were applied in every 
conceivable way and unfortunately much harm has been done to the 
rational use of vaccines by reckless commercialism. 

Wright and his collaborators have studied carefully the opsonic 
index of patients the victims of infectious disease as well as that of 
normal individuals. They found that phagocytosis is often depressed 
in those who are unsuccessfully combating certain disease and that the 
phagocytic power can be increased by specific bacterial vaccination. 
They pointed out further that following the first dose of vaccine the 
opsonic index is considerably depressed and spoke of this phenomenon 
as the negative phase. This phase may last or several days and 
numerous writers have thought that such a depression of phagocytic 
resistance might indicate such a decrease of general immunity as to 
render vaccination during an epidemic highly undesirable. The nega- 
tive phase has been carefully investigated and many now believe that 
it does not exist. The factor of error in the determination of the 
opsonic index is considerable, owing to the variability of conditions 
operating in vitro. Therefore, it is possible that the decrease of index 
pointed to by Wright may fall within the limit of experimental error. 
The recent observations of Balteano and Lupu indicate that no such 
negative phase is demonstrable in cholera, and the careful investiga- 
tions of Cantacuzene indicate that the negative phase does not occur 
in other diseases. 

Types of Vaccines. Living Vaccines. From animal experiments 
it is generally admitted that the greatest and most lasting immunity is 
produced by the injection of living bacteria. The killing of bacteria 
apparently destroys certain thermolabile substances which possess anti- 
genie properties. In human practice the use of living bacteria is not 
without danger. One may at first inoculate with a single living organ- 
ism and cautiously increase the number, but the virulence of the organ- 
ism is not easily controlled and may be so great as to make such 
inoculations dangerous. In addition there is a risk of establishing a 
" carrier state " since the gradual increase of the number of organisms 
may establish a mutual immunity on the part of both the parasite and 
the host. If the virus of the disease can be so attenuated that danger 
of producing an outspoken attack of the disease is eliminated, vac- 
cination can be performed with great success. The outstanding ex- 
amples of this method in human medicine are vaccination against 
smallpox and against rabies. In smallpox the virus is attenuated 
by animal passage through the calf and in rabies the virus is attenuated 
by desiccation. 

Sensitized Vaccines. These are bacterial vaccines composed of 
"bacteria which have been exposed to their specific immune serum. As 
early as 1891 Babes mixed the blood of a highly refractory dog with 
an emulsion of street virus in order to produce in other animals a more 


rapid development of immunity against rabies. In the only experiment 
reported at this time it was shown that some protection was afforded 
by the mixture, although the inoculated animal finally succumbed to 
rabies. Lorenz in 1892 made similar observations in swine erysipelas. 
Since this time numerous workers have used the method. The most 
important advance was made when Besredka suggested the removal 
of the excess of serum by centrifugally washing the sensitized bacteria. 
Subsequent work has been carried on with killed bacteria treated with 
their immune sera, washed and suspended in a suitable menstruum. 
The ordinary non-sensitized bacterial vaccines injected into an animal 
during the incubation period of a disease are likely to hasten the death 
of the animal, or if the infection is already acquired, the injection of 
the vaccine appears to lower the natural resistance. Besredka and 
Metchnikoff believe that sensitized bacterial vaccines produce no nega- 
tive phase, but only slight local and general reactions and facilitate the 
production of antibodies. Kakechi has shown that the toxicity of 
sensitized bacterial vaccines is less than that of the non-sensitized. 
Sensitized bacterial vaccines have been employed in numerous infec- 
tious diseases such as typhoid fever, asiatic cholera and bubonic plague 
with varying degrees of success. 

Killed Bacterial Vaccines. These are suspensions of bacteria usu- 
ally in salt solution but sometimes in other mentsrua such as neutral 
oil. The organisms are usually killed after the suspension has been 
made, but in making oil suspensions the organisms are killed before 
the final suspension. Heat is usually employed for killing the bacteria 
and the action is further supplemented by the addition of a bactericidal 
preservative to the suspension. Under certain circumstances chemicals 
such as formaldehyde or phenol may be employed both for killing and 
preserving the vaccine. Autogenous vaccines are bacterial vaccines 
prepared from bacteria which have been freshly isolated from the 
individual patient. At times it is very difficult to isolate the organism as 
for instance in gonorrhea. In these cases stock vaccines are usually 
employed. Stock vaccines are made from strains of bacteria isolated 
at some previous time and kept in the laboratory stock. Stock vaccines 
are used extensively in prophylactic vaccinations. Mixed vaccines are 
composed of various kinds of bacteria. Their value is questionable 
and their use unscientific, except on the basis of non-specific therapy. 
Many efforts have been made to produce the bacterial antigen in a pure 
form so as to obtain a minimum of local and general reaction, and to 
immunize in the shortest space of time possible. Such vaccines have 
been made from nucleoproteins, autolyzed bacteria, digested bacteria 
and detoxicated organisms. It appears that some of these methods are 
promising, especially for the production of antigens from spore- 
bearing bacteria. 

Preparation of a Bacterial Vaccine. Under strict asepsis an emulsion of 
the organism in question is prepared by adding 5 to 10 c.c. of physiological salt 
solution to a twenty-four-hour agar slant culture. This is allowed to stand ten 
minutes and then rotated actively in order to make a suspension of the organisms. 
The suspension is now filtered through sterilized filter paper in a funnel into a 


sterile test-tube. In case of scanty growth the emulsion is directly transferred 
to another surface culture, the growth in this tube suspended and the process 
repeated with additional growths until a satisfactory 'emulsion is obtained. 
Instead of filtering the emulsion one may shake the emulsion in a test tube 
containing glass beads to break up the clumps. It is of great importance to have 
a homogeneous suspension. Because of the presence of pepton or proteins 
from the culture media some authors advise washing of the organisms until the 
supernatant fluid gives a negative biuret reaction. The next step in the prepara- 
tion is the counting of the 'emulsion. This can be done by the hemocytometer 
method, by Wright's method and other methods. 

Hemocytometer Method. (From Zinsser, Hopkins and Ottenberg, " A 
Laboratory Course in Serum Study.") A staining solution is prepared by adding 
to 20 c.c. of i per cent, phenol I c.c. of a saturated alcoholic solution of thionin. 
A small amount of the carefully shaken bacterial suspension is removed to a 
watch glass. A dilution of i-ioo is prepared in a red cell pipette with the staining 
solution as diluent to the 101 mark. After carefully shaking and after blowing 
out the portion of the fluid in the capillary end of the pipette a small drop is 
placed in a counting chamber and covered with a flat coverslip. After allowing 
fifteen minutes for the bacteria to settle a count is made, with 4. num. objective, 
of a number of squares until 200 or more bacteria have been counted. It is best 
to take this count from different portions of the ruled surface and from two 
separate drops of the mixture. The small squares have an area of 1/400 of a 
square mm., the depth of the chamber is o.i mm., the dilution is I IOO. The 
number of bacteria may be estimated by the following formula : 

Number of bacteria counted X 400 X 10 X 100 X 1000 

; ; = number of bacteria in r.o c.c. 

Number of squares counted 

Wright's Method. A drawn-out capillary pipette is prepared and marked 
with a grease pencil about 2. cm. from the tip. A small puncture is made in the 
tip of the finger and a fresh drop of blood obtained. Three units of salt solution 
are then drawn up in the pipette, admitting a bubble of air between each unit of 
salt solution. The unit is the amount that is drawn up to the mark on the 
pipette. Blood from the finger-tip is then drawn up to the mark, a bubble of air 
admitted and the bacterial suspension drawn up to the mark. The mixture is then 
blown out on a clean slide and drawn in and out of the pipette several times to 
ensure even mixing of the blood and bacteria. A drop of this mixture is placed 
on a second slide and carefully spread across the slide in the manner of making 
blood smears. It is important that the film be thin and even, so that the red 
cells are not piled in masses in any portion of the film. This film is stained 
with Wright's stain, or by any other simple method, and a differential count of the 
number of bacteria and red cells in a number of fields in different parts of the 
slide is made. For this a rule scale to be inserted in the eyepiece of the micro- 
scope is very helpful. Fields are counted until 200 red cells have been counted. 
The number of bacteria in the suspension may then be estimated from the number 
of bacteria counted, using the following formula (assuming that the blood of the 
worker contains 5.000,000 red cells per cmm.) : 

Number of bacteria X 5,000,000 X 1,000 XT 

^ r r j T; ? \ = Number of bacteria per c.c. 

Number of red cells (200) 

Other Methods. Among the other methods of standardization of the sus- 
pension are the comparison of the emulsion with a known standard emulsion, the 
estimate of the average number of organisms per slope grown in, say, eighteen 
hours, or an estimate of the number of germs per loopful (Kolle's method). 
Hopkins centrifugalized his suspension at high speed in a special tube with 
graduated tip until the supernatant fluid was clear. The number of organisms 
for a number of species in such a closely-packed sediment has been determined 
and is as follows : 

Staphylococcus aureus o.oi c.c. equals 10 billion 

Streptococcus hemolyticus o.oi c.c. equals 8 billion 

Gonococcus o.oi c.c. equals 8 billion 

Pneumococcus (capsulated) o.oi c.c. equals 2.5 billion 

B. typhosus o.oi c.c. equals 8 billion 

B. coli o.oi c.c. equals 4 billion 


Gates recently standardized his bacterial suspension by measuring the opacity 
of the suspension by the length of the column of the suspension required to cause 
the disappearance of a wire loop. By a simple formula the measured opacity is 
translated into terms of the concentration of bacteria per cubic centimeter and so 
made comparable with that of other suspensions of the same organism. 

The stock suspension after estimation of the number of organisms contained 
is ready for dilution. Shera employs the following method for dilution. Suppose 
the suspension is found to contain 6400 million organisms per cubic centimeter, 
and that a vaccine of 1000 millions per cubic centimeters is required. Five cubic 
centimeters are measured out accurately after shaking well, and they are made 
up to 6400/1000 parts, i.e., 6.4 parts. Multiply 6.4 x 5 and the result 32 equals the 
volume in cubic centimeters to which the 5 c.c. should be made up. The suspension 
is sterilized by means of heat. For staphylococci and streptococci 59 to 60 C. 
for half an hour is sufficient ; for typhoid bacilli 50 to 56 C. for an hour is 
usually employed. It is best to add some preservative as phenol or tricresol (0.3 
to 0.5 per cent.) to the suspension and to have the suspension in sealed ampoules 
preferably of brown glass before immersing in the water bath. Connor success- 
fully sterilized his staphylococcic vaccines by means of fluorides. After steriliza- 
tion an ampoule should be opened so that a culture may be made. No vaccine 
should be used until a culture is found to show no growth. If ampoules are not 
at hand they may be made from test tubes or the vaccine may be kept in sterile 
bottles with rubber stoppers or caps. 

Dosage of Organisms. For gonococci, bacillus coli, streptococci 
and pneumococci 5,000,000 to 50,000,000 are usually employed, while for 
staphylococci 200,000,000 to 1,000,000,000. Wilson gives the following 
minimum and maximum doses : Streptococcus, 6 and 68 millions ; 
staphylococcus, 150 and 900 millions; gonococcus, 45 and 900 millions; 
meningococcus, 300 and 900 millions; micrococcus melitensis, 700 and 
1400 millions; bacillus coli, 16 and 240 millions; bacillus typhosus for 
treatment, 100 and 250 millions; bacillus typhosus for prophylaxis, 500 
and 1000 millions; bacillus pyocyaneus, 34 and 1000 millions; bacillus 
pneumonia, 44 millions; bacillus tuberculosis, 1/2000 to 1/200 mg. 

Lipovaccines. Recently LeMoignic and Sezary showed that it is 
possible to obtain as highly hemolytic serum by injecting red cells sus- 
pended in oil as by injecting them suspended in salt solution. They also 
showed that the oil suspension gives slow absorption, and that the oil acts 
as a detoxifying agent. As an example of the rate of absorption it was 
shown that the injection 0.35 mgm. of strychnine in aqueous solution 
kills a guinea-pig, but the injection of six times that amount is harmless 
if the strychnine be dissolved in oil. This led LeMoignic and Pinoy, 
Achard and Foix, and LeMoignic and Sezary to suspend bacterial 
vaccines in oil, and to inject the entire vaccinating dose at one time. 
Bacterial vaccines suspended in saline are rapidly autolized. As 
autolysis advances, absorption following injection becomes more rapid 
and the immediate reaction more severe. Oil vaccines are preserved 
much more easily than saline vaccines and the reactions following 
their injection are less severe. The oil vaccines are known as " lipo- 
vaccines." The bacteria have been suspended in lanolin, lecithin, 
sperm oil and many vegetable oils. Cotton-seed oil is at present widely 
used. It is of great importance to use neutral oils. The sterilization 
of these oils has been a difficult problem and a drawback in the prepara- 
tion of the vaccines. The technic must be strictly aseptic. At present 
lanolin and oils are sterilized in the autoclave at fifteen pounds for 


fifteen minutes. Ultra-violet rays have been used. Chlorine has also 
been employed, but the resulting hydrochloric acid is difficult to remove. 
Whitmore and Fennel used powdered potassium iodid. This was added 
to olive oil and sweet almond oil; iodin was liberated in sufficient 
amount to sterilize the oil, and was taken up in the oil molecule so that 
no free iodin could be detected. Sweet almond oil is sterilized in about 
three days, but it requires about ten days to sterilize olive oil. It is not 
known, however, how the suspension in oil affects the antigenic power 
of the vaccine, but certain workers claim to get better results than by 
the use of saline vaccines. Against the use of lipovaccines is the 
possibility of fat embolism from accidental entrance of the vaccine 
into a vein, but Graham considers this factor of minor importance since 
the amount of oil is small. He injected as much as 0.8 c.c. of oil into 
the ear vein of a rabbit and observed only a slight passing dyspnea 
and no other evidence of discomfort. Care should be taken, however, 
to administer the vaccine subcutaneously and to avoid veins. Drawing 
out the plunger of the syringe after the needle has been introduced 
determines whether or not an important vein has been entered. The 
upper arm beneath the insertion of deltoid muscle is usually selected 
for the injection. The region of the scapular or pectoral muscles 
may do as well. 

Contraindications. In prophylactic immunization it is of im- 
portance to ascertain whether the patient has latent or active 
infection. In active tuberculosis vaccination is considered danger- 
ous. Caution should be observed in diabetes, parenchymatous nephritis 
and carcinoma. 


Smallpox Vaccination. Although inoculation with the virus in 
smallpox in an attempt to produce a mild attack of the disease had 
been practiced for centuries and although for many years it had been 
observed that an attack of cowpox rendered man immune to smallpox, 
it remained for Jenner in 1796 to furnish the scientific proof of the 
efficacy of vaccination with cowpox in the prevention of smallpox. 
Jenner's publications were so convincing that the method soon attained 
widespread use and was introduced into America in 1800 by Dr. Benja- 
min Waterhouse, of Boston. The work of the latter investigator was 
especially well conducted and convincing. In 1894 Copeman demon- 
strated the protection of monkeys against smallpox by vaccination with 
cowpox, and this was subsequently confirmed by Brinckerhoff and 
Tyzzer. The introduction of vaccination following Jenner's publication 
immediately led to marked reduction in the incidence of this disease 
and its mortality. The table on page 279 (taken from O'Connell, " Vac- 
cination ; What It Is, etc.," circular New York State Department of 
Health, 1908) gives a clear indication of the reduction of mortality. 

Up until fairly recent times vaccination was practiced by inocu- 
lating patients with the fragments of the crust obtained from others 
who had been successfully vaccinated. This method has been aban- 



doned because of the possibility of transferring infection in the crusts, 
not the least important of which is syphilis. With the development of 
important Board of Health laboratories and large commercial lab- 
oratories it is now possible to secure cowpox virus in a form free 
from infective organisms. 


Before vac- 

After vaccina- 


Smallpox death rate, per 1,000,000 pop. 

Before vaccination 

After vaccination 



Austria (lower) 





Austria (upper and 











Tyrol and Vorarlberg 















Silesia (Austrian) 





Prussia (East Prov- 






Prussia (West Prov- 











Rhenish Provinces 







I 7 6 











The Preparation of Smallpox Vaccine. For this purpose cow- 
pox is produced in young heifers from two to four months old. The 
animals are taken from selected stock, carefully tested for the presence 
of tuberculosis and observed for several days so as to ensure perfect 
health. The body is cleansed and the abdominal surface shaved from 
the ensiform cartilage to the pubis, extending the area out on the 
flanks and the inner surface of the thighs. The skin is washed with 
soap and water, then with alcohol and finally with sterile water. About 
100 small cuts through the epidermis are made under strictly aseptic 
precautions. If bleeding occurs the blood is carefully wiped away. 
Virus may be obtained primarily from smallpox patients who are 
otherwise healthy. At the present time, however, the virus kept as 
" seed virus " is obtained from previously inoculated animals. Virus 
is introduced into the scarifications usually in the form of a glycerol 
suspension. In about forty-eight hours a reaction appears and by the 
sixth day the vesicles are well rilled with semipurulent material. The 
animal is killed and the vesicles carefully curetted away. After the 
curettage, serum appears and this may be preserved in ampoules or 
small tubes for subsequent vaccination. The pulpy mass . obtained 
by curettage is mixed with four times its weight of a mixture com- 
posed of glycerol 50 per cent., water 49 per cent., phenol i per cent. 
The glycerolated pulp is allowed to stand three or four weeks in order 
to destroy any contaminating bacteria. The pulp is then triturated in 


special machines and sealed in capillary tubes. Formerly " ivory " 
vaccine points were also charged from this pulp, but these have been 
forbidden in interstate commerce (page 282). In all cases the material 
before being prepared for distribution is carefully tested for the 
presence of tetanus bacilli or their spores. Its potency may be deter- 
mined by directly inoculating the inner surface of the ears of rabbits 
and observing the rapidity of the reaction. A somewhat superior 
method is to make dilutions of the virus and to note the effect of these 
dilutions when inoculated on the ears of rabbits. A potent virus should 
produce vesicles in a dilution of i to 500. Efforts have been made to 
secure a virus in purer form and Noguchi has planted the virus in the 
testicles of rabbits and of bulls. Virus recovered from this situation 
is not subject to contamination in the same way as that obtained from 
surface inoculations. The amount of material obtained, however, is 
small and the method has not been used extensively enough to justify 
an opinion as to its value. After preparation of a virus the date 
should be indicated on the container and the material preserved in 
the ice chest. 

Methods of Inoculation in Man. As a rule, vaccination is applied 
on the upper arm over the point of insertion of the deltoid muscle. 
This situation offers protection against injury and contamination such 
as is not afforded by vaccination upon the leg or thigh. The area is 
carefully cleansed with soap and water, followed by alcohol or ether 
and then by distilled water. The last step is sometimes omitted. For- 
merly the area was scarified in a criss-cross manner by means of a 
needle or scalpel, but such extensive scarification has been found to 
be unnecessary and also exposes a greater surface to the possibility 
of infection. The more modern method is to place the virus upon the 
area and to make a scarification through the virus. This may be done 
by a small linear incision, by the drill method or by the multiple punc- 
ture method. Wright has advised intracutaneous inoculation. 

Method of Linear Incision. Af ter placing the virus upon the skin 
a sterile needle or a small scalpel is employed for making a scarification 
through the virus and sufficiently deep into the skin to permit absorption 
but not to produce bleeding. The virus is then gently rubbed into the 
abrasion and permitted to dry. If a dressing is desired it should be of 
sterile gauze loosely applied with adhesive strips after the virus has 
completely dried. Sealing with collodion should not be attempted, 
since it may permit more ready growth of contaminating bacteria 
and produce maceration of the skin. 

The Drill Method. A sterile drill such as is employed in the Von 
Pirquet cutaneous tuberculin test is held between the thumb and middle 
finger. With a twisting motion and moderately firm pressure a small 
abrasion the diameter of the drill is made through the virus. This 
should penetrate the epiderm, but should draw no blood. 

The Multiple Puncture Method. A sterile needle is held nearly 
parallel with the skin and the point placed through a drop of virus so as 


to make an oblique puncture of the epidermis. This is repeated so as 
to produce about six radially disposed punctures, the whole area ex- 
tending not more than about 5 mm. 

The Intracutaneous Method. The virus is diluted to ten times its 
volume with distilled water and injected intracutaneously by means 
of a sterile tuberculin syringe and a fine needle. Two injections about 
2 cm. apart are made. 

All the methods indicated have given equally good results, but 
convenience usually dictates the use of the linear incision or the drill 
method. It is not uncommon in the use of any of these methods to 
make two or three inoculations. 

Vaccinia. Following the inoculation of the virus the areas usually 
remain quiescent for from two to four days when slight reddening and 
itching may develop. Following this a small papule appears, rapidly 
succeeded by the vesicle. It is important to note that the vesicle is 
umbilicated and that its multilocular character is indicated by the 
minute vesicular arrangement of the margin. The vesicle appears in 
from five to six days, rapidly becomes pustular and is followed by the 
formation of the crust. The crust is allowed to drop off and subse- 
quent observations of the scar should show a smooth center, a somewhat 
scalloped edge and more or less discrete minute marginal scars. During 
the height of the local reaction the patient may complain of malaise, 
headache, fever, constipation and other general symptoms. The reac- 
tion of vaccinoid has been discussed in the chapter on Hypersuscep- 
tibility (page 243). 

Immunity as the Result of Vaccination. The extent of immunity 
has been indicated by the decrease in prevalence of smallpox since the 
introduction of vaccination. It may also be measured by the success 
of subsequent vaccinations. Kitasato has revaccinated a series of 931 
cases with successful results as follows : 

After i year 14 per cent. After 6 years 64 per cent. 

After 2 years 33 per cent. After 7 years 73 per cent. 

After 3 years 47 per cent. After 8 years 80 per cent. 

After 4 years 57 per cent. After 9 years 85 per cent. 

After 5 years 51 per cent. After 10 years 89 per cent. 

It will thus be seen that more than 50 per cent, of individuals are 
susceptible to revaccination four years after the original vaccination. 
Millard states that the Government reports of the German Confederacy 
show 91 per cent, to 93 per cent, successful revaccinations in ten years 
or more after the primary vaccination and concludes that " immunity 
acquired through vaccination begins to disappear at about the second 
year and by the tenth year it disappears almost completely." Other 
investigators have obtained similar results. King reported that in 
ninety-six adults who had suffered from smallpox at various ages and 
showed numerous scars of the disease, vaccination was successful in 
75 per cent. These figures indicate that the older conceptions of the 


durability of the immunity produced by vaccination are inaccurate. 
In order to secure satisfactory immunity, vaccination should be re- 
peated at intervals of a few years. In those communities where small- 
pox is endemic vaccination should be repeated every year. In the 
presence of epidemics, an unsuccessful vaccination should not be inter- 
preted as indicating immunity and should be repeated at intervals of a 
week or ten days until successful. We feel that no dependence can 
be unqualifiedly placed on the signs of immunity as indicated by 
Force (page 243). 

Unfavorable Results of Vaccination. If human virus be employed 
the chance of inoculating syphilis must be considered, although the 
danger is slight. Reports of tetanus following shortly after vaccina- 
tion have not been particularly well founded and examination of a 
large number of samples collected by the Hygienic Laboratory in 
Washington by McCoy and Bengston failed to demonstrate the pres- 
ence of the bacilli or their spores in filled capillary tubes, seed vaccine 
or in bulk glycerolated vaccine. " Ivory points " were found to be 
contaminated as delivered from the manufacturer of the points, as well 
as after sterilization and charging. McCoy states that " the sale of 
vaccine virus on or with points in interstate traffic has been prohibited 
by an order of the Secretary of the Treasury." 

The most important source of trouble is the result of vaccination in 
unclean skin, the use of unclean dressings or other failures of asepsis, 
more particularly those resulting from carelessness on the part of the 
patient. Such infections usually remain localized but confuse the 
interpretation of results and may in rare instances become gen- 
eral infections. 

Vaccination Against Rabies. The cause of rabies is probably a 
sporozoan parasite discovered by Negri and named by Calkins " neuro- 
ryctes hydrophobise." Work with this parasite is difficult because of 
failure to isolate the organism in suitable form. Therefore, the investi- 
gations have been conducted with pathological material containing the 
organism. It is found in greatest amounts in tjie nervous system and 
accordingly the brain or cord is selected for experimental work. This 
material is spoken of as the virus of rabies. Street virus is nerve 
tissue obtained from an animal suffering with the natural disease. It 
is extremely variable in virulence, and for this reason is not employed 
for vaccination of man. Fixed virus is usually the spinal cord of 
rabbits obtained after a long series of rabbit passages. By these animal 
passages the virulence increases and the incubation period decreases 
until a point is reached when the incubation period following inocula- 
tion cannot be further shortened. All mammals are susceptible to rabies 
in different degrees, but birds or reptiles are not susceptible. 

The treatment of rabies in man after it has developed has been 
entirely unsatisfactory by the methods of immunology. Immunization 
of animals to the rabies virus produces an immune serum capable of 
killing the virus. Accordingly it was hoped that such a serum could 


be employed for human rabies, but results attendant upon this method 
of treatment have been unsuccessful. Therefore, at the present time, 
efforts are directed toward producing an active immunity in those who 
have been exposed to the disease. It is of interest to note that laboratory 
inoculations in man rarely, if ever, lead to the development of the 
disease. It is probable that in order for infection to occur the virus 
must be implanted with animal sputum or some other form of con- 
tamination. Bites from rabid dogs are relatively infrequent, and it is 
therefore unnecessary to immunize an entire population. Further- 
more, man is somewhat resistant to infection with rabies. Statistical 
evidence in regard to the frequency with which rabies follows the bites 
of rabid dogs are unreliable because of uncertainty as to whether or 
not the animal was rabid. Doebert found that in Prussia, where data 
had been very carefully collected, there was a mortality of 14.8 per 
cent, in 122 untreated persons bitten by rabid animals between the years 
1902 and 1907. Other estimates conform closely to this. More recently, 
however, Marx has expressed the opinion that the rate of mortality 
probably does not exceed 6 per cent, to 10 per cent, of untreated 
bitten persons. The mortality and morbidity rate are practically identical. 
Fortunately the period of incubation of rabies is of sufficiently long 
duration so that active immunization may be effected during the period 
of incubation. 

The period of incubation in man is variable and depends to a con- 
siderable extent upon the site of the bite or scratch. According to 
Bauer, the average period of incubation in 510 cases was seventy-two 
days. In very rare cases the period of incubation may be less than 
nineteen days and in more rare instances it may be one year or more. 
Of seventy-three cases of bites about the head and neck the average 
incubation was fifty-five days ; of 144 cases of bites on the upper 
extremities the average period was eighty-one and one-half days ; 
and of seventeen cases of bites on the lower extremities the average 
period of incubation was seventy-four days. 

Active Immunization. Preparation of Material. As has been 
indicated above it is necessary, because of the failure of passive 
immunization, to produce an active immunization. In spite of the fact 
that laboratory accidents practically never lead to the development of 
rabies it is considered dangerous to inoculate man with the living virus. 
Ferran and subsequently Proescher have, however, employed a method 
whereby the active fixed virus is employed. Both these investigators 
stated that no accidents had followed the use of unmodified fixed virus. 
Hogyes has successfully employed dilutions of fresh fixed virus. The 
majority of investigators, however, have employed virus which has 
been attenuated by a variety of methods including heat, partial diges- 
tion, the action of bile, the action of glycerol, of anti-rabic serum, of 
phenol and of mechanical disintegration. Nevertheless, the original 
method of Pasteur is employed almost uniformly throughout the world. 
For this purpose the virus is passed through rabbits until it acquires 


its minimum period of incubation. The material is introduced into the 
anesthetized rabbit by subdural inoculation. The injection is made 
through a small trephine opening just back of the eye and to one side 
of the median line. The injected material is ground with a small 
quantity of I per cent, phenol solution and 0.2 c.c. of this emulsion is 
injected. After the rabbit is completely paralyzed it is killed with 
chloroform and the spinal cord removed aseptically. A small ligature 
is placed around one end of the cord and the cord hung in a sterile 
bottle in the bottom of which has been placed sticks of potassium 
hydrate. The bottle is placed in an incubator maintained at 22 to 23 C. 
Pieces i . cm. in length are cut off at daily intervals and placed in glycerol 
where the degree of virulence on that particular day is retained for 
several weeks. In large laboratories animals may be killed on suc- 
cessive days and the whole cord employed in preparing the material 
for human protection. In the United States Hygienic Laboratory 
pieces 0.5 cm. in length emulsified with 2.5 c.c. of salt solution serve 
for one injection. 

Inoculation in Man. The determination as to who shall receive 
anti-rabic treatment is often difficult, but skilled veterinarians are 
able to diagnose rabies in dogs almost invariably. Knowledge of the 
condition of the animal inflicting a bite is of the utmost importance. 
Although cats and rats are not uncommonly victims of rabies, this is 
not frequently a source of infection in man. When a dog bite is re- 
ceived, the animal should be captured and observed for at least two 
weeks, during which time the symptoms of rabies become manifest. 
If the animal is killed the brain should be sent in glycerol to the nearest 
laboratory, where it may be examined for Negri bodies. If these are 
not found, material should be injected into rabbits. Negative findings 
in regard to Negri bodies in the dog's brain are not to be accepted as 
evidence. In our opinion it is wise to administer treatment to all 
individuals who have been bitten by animals showing any signs of 
rabies. The material may be supplied to the physician either in the 
form of small pieces of cord to be emulsified in salt solution or in the 
form of an emulsion for dilution with salt solution. The injections 
are given subcutaneously under the skin of the abdomen. If a con- 
siderable time has elapsed since the bite or if the bite has been inflicted 
upon the head or neck the so-called intensive method 1 of treatment is 
adopted. Under other circumstances the mild treatment may be given. 
When material is requested from a commercial laboratory or a state 
laboratory it is necessary to indicate which form of treatment is desired. 
As an example of the two methods, the scheme of treatment as shown on 
page 285, adopted by the New York City Board of Health, will serve. 

The Effects of Treatment. Local reactions are frequent and are 
likely to be severe about the eleventh and nineteenth days of inocula- 
tion. These are urticarial in character and the more severe reactions 
may be accompanied by mild constitutional symptoms. The glycerol 
contained in the emulsions not infrequently produces severe pain for 


a few moments at the site of inoculation. The treatment, although 
practically safe, is not entirely free from danger. Remlinger in a 
study of 107,712 cases that had received treatment found forty cases 
which developed paralysis of the extremities and two of these ter- 
minated in death. The cause of this paralysis is not clear. Certain 
authorities maintain that the virus contains a toxin and that this may 
lead to lesions of the nerves. The mass of evidence, however, is 
against rather than in favor of the conception that toxin plays any 
important part in the virus of rabies. It is also possible that the 
repeated injections of foreign protein may have some influence. Such 
accidents are extremely rare and should not interfere with a decision 
concerning administration of the treatment. 


Day Mild treatment Intensive treatment 

ist 14 and 13 day cord 12 and n day cord, repeat 

in afternoon 

2nd 12 and II day cord 10 and 9 day cord; 8 and 7 

day cord in afternoon 

3rd 10 and 9 day cord 6 day cord 

4th 8 and 7 day cord 5 day cord 

5th 6 day cord 4 day cord 

6th 5 day cord 3 day cord 

7th 4 day cord 2 day cord 

8th 3 day cord 4 day cord 

9th 2 day cord 4 day cord 

10th 4 day cord I day cord 

nth 3 day cord 4 day cord 

I2th 2 day cord 3 day cord 

I3th 4 day cord 2 day cord 

I4th 5 day cord 4 day cord 

I5th 2 day cord i day cord 

i6th 4 day cord 4 day cord 

i7th 3 day cord 3 day cord 

l8th 2 day cord 2 day cord 

I9th 4 day cord 4 day cord 

2Oth 3 day cord 3 day cord 

21 st 2 day cord 2 day cord 

Results of Treatment. The benefits of this form of treatment 
depend to a certain extent upon the time when the injections are begun 
and also to a certain extent upon the situation of the bite. Granting 
that fatalities occur in from 6 to 16 per cent, of untreated bitten indi- 
viduals, the reports of fatalities in from .46 per cent, to 1.25 per cent, 
of treated cases show markedly beneficial effects. More recent statistics 
are highly encouraging. During the year 1916 Viala reported that 654 
persons were treated at the Pasteur Institute with but one death. 


Vaccination Against Typhoid and Paratyphoid Fevers. Al- 
though various investigators had appreciated the possibility of active 
immunization against typhoid fever, this subject was first placed on a 
practical basis by Wright in 1896. In the subsequent year Wright 
and Semple described in detail a satisfactory method for vaccination. 


They employed broth cultures of bacillus typhosus two to three weeks 
old, killed by heating to 63 C. for one hour and preserved with 0.5 
per cent, phenol. The vaccine was treated for sterility, standardized 
and employed in doses of 750 to 1000 million organisms. In the same 
year Pfeifrer and Kolle reported the demonstration of specific anti- 
bodies following the immunization of man against the organism. Since 
that time vaccines have been prepared in a large variety of ways and 
preventative vaccination is now upon a highly satisfactory basis. Vac- 
cination has been employed in military and civil life and has resulted 
in a marked decrease in morbidity and mortality. The results obtained 
in all civilized countries constitutes one of the greatest achievements 
resulting from the study of immunology. 

Preparation of Vaccines. The organisms may be grown in broth or 
upon agar. The broth culture or a salt solution suspension of an agar 
culture may be killed or attenuated. The application of heat or chemi- 
cals for the purpose of killing the organisms reduces in a certain 
measure their antigenic value. If they are dried before being heated, 
temperatures of 120 to 150 C. reduce the antigenic property very 
little. Gay, however, points out that the measure of the antigenic value 
depends upon the determination of different antibodies such as agglu- 
tinins and bacteriolysins, but he notes that this offers "an indication 
rather of the reaction of the animal body than a sure means of deter- 
mining the degree of protection that has actually been afforded." 
Numerous investigators have suggested the use of living bacteria, but 
the knowledge that typhoid fever may exist as a septicemia without 
intestinal lesions offers an objection, to the introduction of living or- 
ganisms. It has been found extremely difficult to attenuate without 
killing the bacteria, but it has been recommended that low degrees of 
temperature, for example 53 C. (Leishman), the use of ether, alcohol, 
various sugars and other chemical and physical agents may kill the 
organisms without markedly reducing the antigenic properties. Certain 
investigators have also suggested the employment of bacterial extracts, 
but this method has not been widely employed. Gay and his collab- 
orators (page 301) have claimed success in the therapeusis of typhoid 
fever by the use of sensitized vaccines and have found that active 
immunization progresses very satisfactorily, according to measurements 
of specific antibodies, yet this method, if employed for vaccination, 
is expensive and probably does not give sufficiently superior results to 
justify its employment in large numbers of individuals. 

It is now recognized that the typhoid bacillus may be divided into 
a number of strains on the basis of cultural and immunological prop- 
erties. In certain countries, including the United States, a single strain 
of the organism has been employed for vaccination, but in others a poly- 
valent vaccine has been employed, the French using ten strains, The 
organisms are grown on large agar surfaces, emulsified in salt solution 
and killed by heat. They are then standardized and a preservative, 
such as phenol, lysol or f onnaldehyde, added. Twenty-four hours sub- 


sequently cultures are made to determine the sterility of the vaccine. 
Standardization is usually on the basis of 1000 million organisms per 
cubic centimeter. If it be desired to give a smaller number of organisms, 
fractions of a cubic centimeter may be employed. It is the practice in 
commercial houses to place specified doses in small ampoules so that 
the physician may administer for each dose the contents of a single 
ampoule. In military practice the vaccine is placed in small bottles with 
a rubber cap so that a needle may be thrust through the cap and the 
required amount of vaccine withdrawn into a syringe. 

As the paratyphoid fevers have been studied, it has been considered 
advisable to vaccinate against these at the same time as against typhoid 
fever. Therefore, vaccines are now prepared containing the bacillus 
typhosus, bacillus paratyphosus A and bacillus paratyphosus B. It has 
been customary to introduce smaller quantities of the paratyphoid 
bacilli so as not to increase to an unfavorable degree the bulk of for- 
eign protein injected. Accordingly for each 1000 million typhoid bacilli 
there are usually added 500 million each of paratyphoid A and B. The 
actual numbers, however, vary in different countries. Castellani rec- 
ommends the addition also of cholera vibrios. This transforms the 
triple vaccine into a tetra vaccine. In northern latitudes this is not of 
particular importance. 

As has been indicated, the organisms are usually suspended in salt 
solution, but recently neutral oil, such as commercial cottonseed oil, 
has been employed for suspension. For such suspension the organisms 
must be very carefully dried before being emulsified in the oil. These 
lipovaccines have the advantage of being administered in one dose and 
of producing little or no reaction. They produce immunity following 
a single injection because of the slow absorption of the oil and its 
contained antigen. 

Method of Administration. In the case of the lipovaccines a single 
large dose of organisms may be administered. The use of the salt 
solution suspensions involves several injections. As a rule, the first 
dose contains 500 million typhoid bacilli and 250 million each of para- 
typhosus A and B. The second and third doses contain 1000 million 
typhoid bacilli and 500 million each of the paratyphoid bacilli. The 
time between injections has been the subject of considerable study, but, 
as a rule, a period of seven to ten days intervenes between these injec- 
tions. Subcutaneous administration is practically universal. Intra- 
venous injections have been recommended, but this method is not widely 
practiced. Lumiere and Chevrotier have administered by mouth gela- 
tine-coated pills of a dried mixed polyvalent typhoid colon vaccine. It 
is probable that this method is not effectual, since the bacterial protein 
must undergo at least partial digestion in the intestinal tract. Bes- 
redka, however, has recently demonstrated in animals the possibility 
of successful vaccination through the intestinal tract, but his animals 
had previously been given bile, and it seems likely that this substance 
produced sufficient lesion of the intestinal mucosa to permit of 
direct absorption. 



Prophylactic Value of Vaccination. It can readily be understood 
that the control of individuals in armies offers excellent facilities for 
determination of the prevalence and mortality of infectious disease. 
Consequently, much of the statistical evidence favorable to typhoid 
vaccination has been collected in armies. The following table, taken 
from Gay, "Typhoid Fever," illustrates the prevalence of typhoid fever 
in Great Britain and her colonies before vaccination was introduced : 


Locality Morbidity Mortality 

Great Britain 120 24 

Gibraltar 420 132 

South Africa 3290 577 

India 3600 1000 

Egypt 8100 2340 

Gay states that even greater rates of typhoid morbidity have been en- 
countered. The results of anti-typhoid vaccination are splendidly 
summarized in another table from Gay's work : 












India 1900 . . . 
















Report of the 
anti- typhoid 
London, 1913 

India 1909 
India 1910 
Various colonies 
IQI V . 

The results obtained in the United States Army under the direction 
of Colonel Russell and his staff have been most impressive. In Decem- 
ber of 1919 Colonel Russell summarized the results in a paper in the 
Journal of the American Medical Association. He gives an analysis 
of a water-borne epidemic in Hawaii as follows : 


Population No. of 

on Castner cases 

water of 

system typhoid 

Vaccinated 4087 55 

Unvaccinated 812 45 





Number Per cent. 






It is of importance to note in reading this table the large number 
of vaccinated as contrasted with the Unvaccinated. It is apparent that 
the vaccinated show not only a reduced morbidity percentage, but also 
a diminished mortality rate. Colonel Russell gives the following table 
of figures from the United States Army for nineteen years : 





No. of cases 

Ratio per 


Ratio per 



IQOO. . . 






I9OI . . 






O 54. 

IQO2 . . 






IQCM. . 






IQO4.. . 












1006. . , 






IQO7. . 






IOO8. . 






" * 





O 2\ 

I9IO . ... 




o. 16 


o ^d. 







IQI2. . 





o 18 

IQI7 . 











O.I 5 






o 18 

O 17 

1916 . . 





O 12 

O 15 







O Id 







O.I I 

* Indicates voluntary vaccination against typhoid. 

{Indicates compulsory vaccination against typhoid. 
Civil deaths from typhoid fever; age group, 20 to 29 years. Rate per thousand of population. 

The marked change after the introduction of compulsory vaccination 
in the Army in 191 1 is most striking. It is pointed out that the increase 
in 1917 is in large part contributed to by delay in the vaccination and 
sanitary control of National Guardsmen. As an impressive contrast 
the following table illustrates the vast improvement in health condi- 
tions as compared with previous wars : 


Typhoid fever 



Number of deaths 

that occurred in 
the World War, 
Sept. i, 1917- 
May 2, 1919. 
Average strength 
appro ximately 

Number of deaths 
that would have 
occurred if the 
Civil War death 
rate had obtained 

Number of deaths 
that would have 
occurred if the 
Spanish- American 
War death rate 
had obtained 











* Includes malaria, remittent and congestive fevers, 
t Includes dysentery and diarrhea. 

During the period of the American participation in the World War 
there were 1065 cases of typhoid fever in approximately 4,000,000 
troops, a ratio of one case to every 3756 men. In the Spanish-American 
War there was one case to every seven men. Colonel Russell's final 
comment is of the greatest interest. "It is evident from these tables, 
therefore, that anti-typhoid vaccination, carried out as it was by a per- 
sonnel which had not been carefully trained in its administration, gave 
a high degree of protection to our forces under the conditions of hur- 
ried mobilization and of warfare, and reduced the rate, not only below 


the rates for previous wars, but also below the rate found in civil life in 
some of the older states where the entire population is protected by all 
the sanitary measures of modern life." 

At the beginning of the World War, of the troops in Belgium only 
those of the British Army were adequately protected. At the beginning 
of trench warfare in 1914 an epidemic broke out, and in January and 
February of 1915, 4000 cases occurred in Dunkirk. Up to May of 1915 
only 827 cases were contributed from the British Army, the bulk of the 
cases came from among the unvaccinated Belgian soldiers and civilians. 
Vaccination was instituted in February, and the epidemic was at an 
end by the middle of the summer. In the early days of the war vac- 
cination had not been compulsory in the French Army, and as the 
result a large number of troops were victims of typhoid fever. The 
institution of vaccination completely altered the picture. Courmont 
gives the following statistics for the French Army in 1916 : 


Non-vaccinated cases 17.4 per cent. 

Of the vaccinated cases: 

Those who had one injection 6.0 per cent. 

Those who had two injections 4.0 per cent. 

Those who had three injections 2.5 per cent. 

Those who had four injections 1.9 per cent. 

Duration of Protection. When typhoid vaccination was first in- 
troduced it was generally assumed that protection lasts for about two 
years. Certain British troops in Mudros were found to have developed 
typhoid fever within six months after inoculation. Similarly, certain 
troops of the American Army developed typhoid fever a few months 
after they had been vaccinated, but it was found upon investigation 
that in this instance the vaccination had not been completed. On the 
basis of experience, yearly vaccinations were practiced in the British 
Army, although it was not considered necessary to give the three 
doses at the time of revaccination ; a single maximum dose on revac- 
cination apparently served to maintain immunity. Yearly revaccina- 
tion, however, provides adequate protection. Knowing that infection 
has occurred within a few months after proper vaccination it is no 
longer advisable to state that protection lasts for more than a year. 
The determination as to when revaccination must be practiced depends 
in certain measure upon the degree of exposure to the disease. In 
those districts where typhoid or paratyphoid fevers are endemic, we rec- 
ommend that vaccination be reinforced by a single yearly inoculation of 
the maximum dose. If a period of two years has elapsed since previous 
vaccination, it is advisable to revaccinate with three injections. 

Complications. The reaction to any dose of typhoid vaccine is 
extremely variable. Usually the second and third doses produce some- 
what more severe reactions than the first dose. There are, however, 
certain individuals who are apparently hypersusceptible to typhoid pro- 
tein, and these may react with great severity. As a rule, reactions are 
merely local and are exhibited by swelling, redness, tenderness and pain 
about the site of inoculation. General reactions are much less fre- 


quent and are exhibited by malaise, headache, fever, constipation and 
occasionally chills. Maurange investigated the general reaction fol- 
lowing 39,215 inoculations and reports the following results: 

Types of reaction JJ*** ^S? 

None 92.23 98.59 

Feeble 6.18 1.41 

Moderate 1.40 0.00 

Pronounced 0.19 o.oo 

Rarely the inoculations may be followed by arthritis, nephritis and 
severe intestinal disturbances. Chantemesse has called attention to the 
recrudescence of tuberculosis during immunization, and it has further 
been suggested that other chronic diseases, including syphilis, may be 
excited to renewed activity. We have observed cardiac arrhythmia in 
individuals who have previously suffered from myocardial disease. 

Contraindications. The contraindications include kidney disease, 
diabetes, myocardial and endocardial disease, aortitis, cachexia, gastro- 
intestinal disturbances and alcoholism. The presence of acute infec- 
tions is also regarded as contraindicating vaccination. According to 
Maurange, age is no contraindication, although the relative unsuscep- 
tibility of old people to typhoid fever may make it seem unnecessary to 
vaccinate. Menstruation is not a contraindication. 

Vaccination Against Cholera. This was first employed by Ferran 
in 1884. Haffkine published results in 1888, .and since then numerous 
investigations have developed technical methods and have emphasized 
the value of protective vaccination. Ferran injected broth cultures of 
living vibrios subcutaneously, employing 0.25 c.c. as the first dose and 
0.5 c.c. as the second and third doses. Haffkine employed two kinds 
of vaccine, a weaker vaccine prepared from living organisms grown 
on agar at 39 C. and a more virulent vaccine prepared from vibrios 
which had been passed through a series of guinea-pigs. Subsequently 
Kolle prepared a vaccine made from heat-killed agar cultures of viru- 
lent organisms. The emulsion is made by suspending 2 mg. organisms 
in saline and heating to 60 C. for one hour. Cantacuzene prepared a 
vaccine by heating emulsions of the vibrios for one and one-half hours 
at 55 to 56 C. The concentration of this vaccine was 500 to 1000 
million organisms per cubic centimeter. Two inoculations were given, 
the first of 2. c.c. and the second of 4. c.c. with a six-day interval. 
Strong prepared a vaccine by incubating the emulsion in sterile water, 
thereby breaking up the cells. The emulsion was then passed through 
a Reichel filter and the sterile filtrate employed. At the present day 
heat-killed vaccines are most commonly employed. 

Results. The earlier work of Ferran and of Haffkine was ex- 
tremely encouraging, but the subsequent statistics lend even greater 
support to the value of this procedure. Arnaud made a study of 
108,000 men during the second Balkan War. These men were all in 
infected areas. Among the unvaccinated men the morbidity was 5-75 
per cent. Among those who had received insufficient vaccination it was 
3.12 per cent, and among those who had received the full treatment it 


was 0.41 per cent. Kobe made an extensive study of the population 
of Tokio and its suburbs. In the city of Tokio, 10.54 per cent, of the 
entire population were vaccinated. The absolute number that were 
vaccinated, namely, 238,936 in Tokio and 61,988 in the suburbs, as well 
as the large number of controls, provides a sufficient number from 
which to draw satisfactory conclusions. In Tokio cholera occurred in 
1.85 per 10,000 of the unvaccinated and 0.13 per 10,000 among the vac- 
cinated. In the suburbs cholera occurred in 3.09 per 10,000 of the 
unvaccinated, and there were no cases reported among the vaccinated. 
Cantacuzene has studied results obtained in the campaigns in the Orient 
during the Balkan Wars and the World War. These were conducted 
particularly during the epidemics, and by a study of the normal curve 
of epidemics he finds that vaccination leads to a sharp drop in the 
epidemic curve and incidence of the disease. 

Vaccination Against Pneumonia. Although vaccination against 
pneumonia was practiced by Wright before the various types of pneu- 
mococci had been identified, it was not until the types were carefully 
studied that exact results could be obtained. Lister, after he had iden- 
tified the types of organisms present in South Africa, carried out 
prophylactic immunization in 11,000 workers in the Rand mines. He 
employed a composite vaccine prepared from the pneumococcus types 
prevalent in that region. He found that subcutaneous inoculations were 
sufficient to establish an immunity, and demonstrated that the pro- 
tection was effective against the particular type of pneumococcus used 
in the vaccines. He emphasized the importance of using a large bulk 
of organisms and considers that the minimum effective dose is at least 
6000 million pneumococci of each group against which protection is 
sought. The work of Cecil and Austin and of Cecil and Vaughan has 
been of the utmost importance. Cecil and Austin employed a saline 
suspension of killed pneumococci of Types I, II and III. Three or 
four doses were given at intervals of five to seven days. The first dose 
contained 1000 million of each of the three types; the second contained 
2000 million of each type, and the third and fourth contained 3000 
million each of Types I and II and 1500 million Type III. At Camp 
Upton 12,000 troops were vaccinated, and among these only seventeen 
cases of pneumonia of all types developed, including those due to 
Type IV as well as to the streptococcus. Among the 20,000 unvac- 
cinated men, 172 cases were reported. At Camp Wheeler a lipovaccine 
was employed containing 10,000 million each of Types I, II and III per 
cubic centimeter, given in one dose. Eighty per cent, of the total com- 
mand, or 13,460 men, were vaccinated and 363 cases of pneumonia of all 
varieties developed. The study was difficult because of the prevailing 
influenza epidemic. An analysis of the records shows that " there were 
thirty-two cases of Types I, II and III pneumonia among the vaccinated 
four-fifths of camp, and forty-two cases of pneumonia of these types 
among the unvaccinated one-fifth of camp. If, however, all cases of 
pneumonia that developed within one week after vaccination are ex- 
cluded from the vaccinated group, there remain only eight cases of 


pneumonia produced by fixed types, and these were all secondary to 
severe attacks of influenza. This exclusion is justified by the fact that 
protective bodies do not begin to appear in the serum until the eighth 
day after injection of pneumococcus lipo vaccine." " The pneumonia 
incidence rate per 1000 men during the period of the experiment was 
twice as high for unvaccinated recruits as for vaccinated recruits, and 
nearly seven times as high for unvaccinated seasoned men as for 
vaccinated seasoned men." The death rate for vaccinated men, in whom 
the pneumonia developed more than one week after vaccination was 
12.2 per cent., whereas among the unvaccinated troops it was 22.3 per 
cent. The death rate for primary pneumonias wasi only one-third as 
great among vaccinated men as among unvaccinated, but the rate in 
pneumonia secondary to influenza was about the same for both groups. 
Among the 20 per cent, of the command which were unvaccinated 327 
cases were reported. These statistics were sufficiently encouraging to 
introduce vaccination into the army on a fairly large scale. Neverthe- 
less, the results are not sufficiently conclusive to state positively that a 
high degree of protection is obtained. Recently Cecil and Blake have 
been able to produce in monkeys a characteristic pneumococcus pneu- 
monia by intratracheal inoculation. These investigators have studied 
the problem of vaccination with saline vaccines and lipovaccines of 
killed pneumococci and in addition have investigated the value of vac- 
cination with living organisms. They found that vaccination with killed 
pneumococci was not effective in preventing the development of the 
disease under the conditions of infection but that the vaccinated animals 
showed a somewhat less severe form of the disease. The living vaccine 
was considerably more satisfactory, but they state that " the method 
is too dangerous for any sort of practical application." Vaccination 
with living virulent pneumococcus, Type I, produces a protective im- 
munity against pneumonia of homologous types. The immunity against 
other types of pneumococcus following vaccination with Type I offers a 
certain degree of protection against other types, but this varies con- 
siderably with the individual monkey. Vaccination with " living aviru- 
lent pneumococcus Type I, if administered in sufficiently large doses, 
renders the monkey immune to a subsequent pneumonia of homologous 
type." Cecil and Blake point out that "vaccination with attenuated 
living pneumococci could probably be practiced with impunity, but the 
problem of transporting and keeping alive large quantities of pneumo- 
cocci in the field would be difficult to solve." 

Vaccination Against Plague. Prophylactic vaccination against 
plague was first reported by Haffkine in 1897. Subsequently Pfeiffer 
and also Gaffky reported experiments which support the value of this 
type of vaccination. HafFkine's vaccine was prepared from a killed broth 
culture of the bacillus pestis five or six weeks old. Adult males were 
given 3 to 3.5 c.c. and adult females 2 to 2.5 c.c. Kolle's vaccine is 
prepared from slant agar growths suspended in the proportion of 2 mg. 
of bacilli to the cubic centimeter of salt solution. Kolle and Strong 
also employed living organisms whose virulence had been greatly re- 


duced. Lustig and Galeotti used nucleoprotein extracted from the 
organisms and Kitano and others have employed organisms grown in 
Bengal isinglass medium. Kitano and Sukegawa employed sensitized 
vaccines and are of the opinion that these give better results than the 
usual heated vaccine. They gave in the first dose 2 mg. of the sensi- 
tized organism and in the second dose 4 mg. of the sensitized organism. 
If haste is essential, 6 mg. may be given at one dose. 

Experimentally, it has been established that vaccinated animals dis- 
play an increased resistance against the disease. The Indian Plague 
Commission reported that vaccination in man diminishes the incidence 
of the disease, but that it does not furnish absolute protection. Appar- 
ently the duration of immunity lasts from a few weeks to a few months, 
but immune bodies are not demonstrable until ten days have elapsed. 
In spite of the fact that numerous investigators have reported favorably 
on vaccination against plague, Flu has stated that an analysis of the 
statistics fails to furnish evidence that sufficient attention has been 
given in the earlier studies to the prevalence of infected rats or to 
other hygienic conditions which prevailed. 

Vaccination Against Typhus Fever. Vaccination against this 
disease has been attempted with the serum of convalescent patients, but 
the results have not been highly satisfactory. Plotz, Olitsky and Baehr 
employed a vaccine composed of fifteen strains of bacillus typhi exan- 
thematici. Of a series of 5251 vaccinated individuals where typhus was 
epidemic only three contracted the disease, and in another series of 
8420 cases only six contracted the disease. Although the work of Plotz 
with this organism has been carefully done there is still doubt as to its 
exact etiological relationship. In statistics concerning this disease, 
the presence of infected lice should be taken carefully into considera- 
tion. It cannot be stated that vaccination in typhus has any great value 
until further investigations have been conducted. 

Vaccination Against Pertussis (Whooping-Cough). The dis- 
covery of the bacillus of whooping-cough by Gengou almost immediately 
led to investigation as to vaccination. Luttinger has summarized the 
results obtained in a large whooping-cough clinic and by over 180 private 
physicians and health officers. The results were sufficiently encouraging 
to justify the recommendation of this procedure. Conditions of ex- 
posure and the nature of surroundings, as well as the variability of the 
disease, even in a single epidemic, makes the interpretation of statistics 
extremely difficult. 

Vaccination Against Dysentery. Prophylactic vaccination against 
dysentery has encountered great difficulties because of the extreme tox- 
icity of the cultures. Shiga attempted to overcome this by employing 
mixed active and passive immunization. He used a bacterial vaccine to 
which was added immune serum. Experiments on 10,000 individuals 
showed a definite decrease in the rate of mortality. Others have em- 
ployed toxin-antitoxin mixtures with apparent success, but Hoffmann 
found that this type of vaccination failed to have any effect on the control 
of a dysentery epidemic which he studied. Whitmore and Fennel and 


also Fennel and Petersen have prepared lipovaccines. It was found pos- 
sible to administer in a single dose 3(300 million Shiga organisms, 3200 
million Y type organisms and 2200 million Flexner organisms without 
marked local or general reaction. In experiments with animals immune 
sera can be prepared with much less difficulty when the organisms are 
administered suspended in oil. The method has not as yet been given 
sufficiently extensive trials in man to justify definite 'Statements as to its 
efficacy, but from the experimental results obtained it appears to have 
more promise than any of the other methods proposed. 

Vaccination Against Influenza. Vaccination against influenza was 
practiced very extensively in the recent great epidemic. The contro- 
versy over the etiological relationship of the bacillus of Pf eiffer has, in 
our opinion, not been settled. The results of vaccination with this 
organism might serve to settle in part the question as to the cause of 
the disease, since a high degree of immunity to the disease following 
vaccination, if interpreted in the sense of specificity, would indicate that 
the organism employed is the exciting cause. The vaccines which have 
been employed have been suspensions in salt solution, killed by heat. 
In certain districts stock cultures have been employed, in others a cul- 
ture of a strain or strains isolated during the epidemic has been used, and 
in still others a mixed vaccine has been used composed of the bacillus 
of Pf eiffer, the streptococcus, the pneumococcus, the staphylococcus and 
other organisms. Reports of striking success following vaccination 
have been numerous, including in particular the work of Duval and his 
collaborators. In consideration of reports of this sort the curve of the 
epidemic has sometimes been overlooked. Reports of certain other 
investigators have not been encouraging. McCoy states that " the gen- 
eral impression gained from uncontrolled use of vaccines is that they 
are of value in the prevention of influenza ; but, in every case in which 
vaccines have been tried under perfectly-controlled conditions, they 
have failed to influence in a definite manner either the morbidity or 
the mortality." At best the method must be regarded as still in the 
experimental stage. 

Vaccination Against Other Diseases. Vaccines have been pre- 
pared against scarlatina, cerebrospinal meningitis, tuberculosis and con- 
taminated wounds. Examination of the statistics presented fails to 
produce convincing evidence that vaccination against these conditions is 
especially satisfactory. As time goes on, methods may be improved 
and larger statistical evidence collected. 






















Introduction. A clear differentiation must be made between 
prophylactic vaccination and therapeutic vaccination. The value of 
various modes of prophylactic vaccination has been discussed and their 
importance in protection against various diseases has been outlined. 
For purposes of discussion of therapeutic vaccination it is well to con- 
sider the infectious diseases as either acute or chronic and either local 
or general. Acute infectious processes are for the most part self- 
limited and require little in the way of specific treatment, and spon- 
taneous cure is so regular as to render difficult the interpretation of 
results following therapeutic vaccination. Chronic infectious diseases 
tend to be progressive and finally result either directly or indirectly in 
the death of the patient. Statistical reports may show instances of 
amelioration of the disease, but the personal bias of the investigator 
may sometimes confuse the conclusion. Generalized infections may be 
treated by simple bacterial vaccination, but the results with sensitized 
vaccines have been better than those with unsensitized vaccines. With 
few exceptions the results of therapeutic vaccination have been best 
in cases of localized infection. The vaccines employed may be in the 
form of stock vaccines, but the opinion is practically universal that 
wherever possible the employment of autogenous vaccines gives the 
best results. 

The persistence of chronic infections is, in part, due to the fact that 
the chronic inflammatory fibrous tissue hinders the general absorption 
of antigenic materials produced by the exciting organism. Conse- 


quently, immune bodies are not produced in sufficient amounts to 
combat the infection. Vaccination may serve to stimulate a general 
immune reaction which aids in the resistance to the local lesion. In 
generalized infections the simple bacterial vaccines may add to the load 
carried by the body and perhaps reduce rather than enhance immunity. 
If, however, immune serum is added to the vaccine or introduced sep- 
arately, the serum may operate either upon the body or upon the 
bacteria so as to favor resistance. 


Vaccine Treatment of Gonorrhea. If stock vaccines are to be 
employed, it is desirable to use those composed of a variety of strains 
of the organisms. Many of the vaccines employed are heated salt solu- 
tion suspensions of the organisms. Demonchy advises the use of large 
doses of unheated salt solution suspensions of stock cultures. Thomson 
has prepared a so-called detoxicated vaccine. In the earlier method 
Thomson dissolved the organism in N/io NaOH and precipitated with 
N.HC1. The toxins remain in the supernatant fluid. Later he found that 
the toxins could be removed by washing with 0.5 per cent, sodium 
acid phosphate and 0.5 per cent, phenol. Haworth employed sensitized 
vaccine, and recently Sezary has recommended lipovaccine. Most in- 
vestigators recommend the employment of large doses of the organ- 
isms, ranging from a minimum of 5000 million to a maximum of 
25,000 million. 

The vaccines have been employed in acute gonorrheal urethritis 
but with relatively little success. They have also been employed in 
vulvo-vaginitis in children, in some instances with apparent success. 
Undoubtedly, the field for therapeusis of this sort is best realized in 
gonorrheal arthritis. In this condition persistent vaccination has been 
followed in many cases by excellent results. Somewhat similar are the 
chronic infections of urethral glands, prostate, seminal vesicles and the 
internal female genitalia. Results from treatment of these conditions 
warrant a trial of vaccine treatment in conjunction with other modes 
of treatment or in those instances where other forms of treatment have 
failed or are contraindicated. 

Cystitis. The organisms which may cause cystitis are variable, but 
in those cases where the disease is chronic and resistant to local treat- 
ment the causative organism usually belongs in the colon typhoid group, 
the bacillus coli communis being the most frequent offender. In treat- 
ment of this disease it is of fundamental importance to discover the 
cause. In cases due to the colon bacillus the vaccine may be given in 
the form of killed salt solution suspensions of organisms isolated from 
the case. Stock vaccines may be employed when necessary. The dose 
is usually from 50 million to 100 million. Results have been extremely 
variable, but the method is sufficiently well established to justify trial in 
resistant cases. Of fundamental importance is the removal of ure- 
thral stricture, prolapse of the bladder or other local conditions which 
retard cure. 


Pyelitis and Suppurative Nephritis. In pyelitis the causative or- 
ganism should be discovered before vaccine treatment is considered. 
If due to the bacillus coli communis, autogenous vaccines in doses of 
from 50 million to 100 million organisms given at weekly intervals 
often yield good results. Suppurative nephritis occasionally is improved 
by vaccination with the causative organism, but the danger of wide- 
spread infection as a result of the disease is so great that in our opinion 
surgical measures are of more immediate importance unless the general 
condition of the patient contraindicates operation. 


Many of the diseases of the skin and of the subcutaneous tissues 
depend upon the local action of bacteria ; a considerable number of these 
is susceptible to vaccine treatment. A greater number of skin diseases 
is the result of more deep seated disorders and under these circumstances 
it is essential that the cause be corrected ; in these instances vaccine 
treatment is of little avail unless the primary disease is one susceptible to 
that mode of treatment. 

Furunculosis. Furuncles are usually caused by some variety of the 
staphylococcus, most frequently the staphylococcus pyogenes aureus. 
Occasionally, furuncles may be the result of streptococcus infections 
or of mixed infections. The single furuncle usually heals after the 
pus is discharged, either naturally or surgically, and may clear up with- 
out any interference whatever. Patients are seen, however, in whom 
furuncles appear repeatedly. In some of these cases the underlying 
cause is diabetes mellitus and in others it is apparently due to a pro- 
longed decrease in the number of circulating leucocytes. Vaccination 
in cases in which the boils are persistent and frequent is usually effec- 
tive. Stock vaccines are frequently employed, but in this condition, as 
in others, autogenous vaccines are to be preferred. Stock vaccines have 
frequently failed because of failure to identify the exact organism 
causing the condition. For example, staphylococcus aureus stock vac- 
cines are employed on the assumption that the boils are due to this 
organism, whereas if cultures were made from the boil another organism 
might be isolated. It is generally recommended that the vaccine be 
composed of 2000 million organisms per cubic centimeter. It is im- 
portant that the first dose be relatively small and the increase in doses 
gradual. At the first dose o.i c.c. is given and at the second dose 0.2 
c.c. is given and the doses increase by gradations of o.i c.c. until the 
maximum dose of i.o c.c. is reached. It is often recommended that 
the doses be given eight days apart, but this period may be reduced 
with advantage to three or four days. In case of diabetes the vac- 
cination should proceed more slowly and with somewhat smaller 
doses than in other cases. With the dosage recommended, local 
reactions are slight and general reactions very rarely appear. Vac- 
cination in furunculosis usually gives excellent results and is to be 
highly recommended. 

Carbuncles. These are also benefited in certain instances by vac- 


cine treatment, but it must be expected that many cases will fail to 
improve. On the whole, surgical treatment is more satisfactory. 

Eczema. The recent studies of this disease have shown that many 
cases are the result of hypersusceptibility to proteins, usually those 
contained in food. Granted that such hypersusceptibility is demon- 
strable, treatment is in the form of immunization to the particular 
protein concerned. Such immunization is similar to that employed 
in hay fever and has been commented on in the chapter on hyper- 
susceptibility (page 231). Kolmer states that the prolonged admin- 
istration of an autogenous bacterial vaccine composed of staphylococci 
procured from the scales or serous exudate has occasionally aided in 
the treatment of obstinate cases of eczema. 

Ringworm. Strickler has recently employed a vaccine made of 
several strains of the fungus and is of the opinion that the method has 
some value in obstinate cases. 

Other Skin Diseases. Vaccination has been employed with a vari- 
able degree of success in the different forms of acne, sycosis, scrofulo- 
derma, impetigo and certain forms of erythema. 


Rhinitis. Vaccination against acute rhinitis has been largely 
prophylactic in nature, and the results of these vaccinations have been 
in a general way favorable. The exact cause of this disease has not 
been finally proven, but the work of Foster indicates rather strongly 
that the agent is a filterable virus. The prophylactic vaccines, however, 
have been mixed stock vaccines of a variety of bacteria, and it seems 
probable to us that any success obtained upon this basis is probably 
non-specific. Coates is of the opinion that if acute rhinitis is treated 
early with vaccines there is likely to be improvement. The course of 
acute rhinitis is so variable that statistical results are open to some 
question. In chronic rhinitis it is maintained that autogenous vaccines 
are of value. It must be understood, however, that contributory causes, 
such as adenoids, enlarged tonsils, polyps and nasal deformities must 
be removed. So much benefit accrues from ,the correcting of the 
contributory causes that the beneficial effects of vaccination probably 
depend in certain part upon the personal equation of the observer. 

Ozena. The cause of this disease is at present a matter of con- 
siderable dispute, and the value of vaccination is undecided. The vac- 
cines that have been employed are usually made from the bacillus 
ozenae fetidae of Perez. Horn claims that this organism is similar to 
the bacillus bronchisepticus and has made polyvalent stock vaccines 
which he claims are highly successful. Friel reports excellent results 
from the intravenous administration of sensitized living vaccine of 
Friedlander bacillus. Ersner has had disappointing results. While im- 
provement may occur in a certain percentage of cases, McKenzie found 
a marked tendency to relapse following the cessation of treatment. 

Asthma. As with eczema, the recent investigations of hyper- 
susceptibility have placed the study of asthma upon an entirely new 


basis. According to the work of Walker and his collaborators, certain 
of the cases are due to specific bacterial invasion, and probably con- 
tributed to by a certain degree of hypersusceptibility to the organism. 
Bacterial vaccination in these cases has been accompanied by good 
results. A complete investigation of the nature of the case is essential 
before any form of vaccine treatment should be attempted. Earlier 
investigators have employed mixed vaccines made of organisms obtained 
from the sputum. 

Pertussis. Prophylactic vaccination against this disease has been 
discussed (page 294). Therapeutic vaccination has been employed by a 
number of workers with, in many instances, apparently favorable re- 
sults. Luttinger found that in a series of 952 cases treated by vaccina- 
tion the paroxysmal stage averaged about thirty-seven days, whereas 
149 cases not treated with vaccine had a duration of over fifty days. 
Blum and Smith found that non-specific vaccination was practically as 
effective as vaccination with the bacillus of Gengou. Barenberg also 
finds that pertussis vaccine, even when given in large doses, has neither 
curative nor ameliorating effect. Kraus and others have reported good 
results by the use of a vaccine prepared from the sputum. The sputum 
is washed, mixed with ether, shaken for three or four days, the ether 
evaporated, the mixture tested for sterility and given in doses of I .o c.c. 
every three or four days. If stock vaccines of the organisms are em- 
ployed, it is of the utmost importance that they be fresh. Doses of 
25 million organisms may safely be given. 

Pneumonia. Prophylactic vaccination (page 292) is distinctly 
more promising than therapeutic vaccination. Treatment with immune 
serum (page 256) is also more promising than vaccination. Coleman 
is of the opinion that vaccines in pneumonia are never harmful and 
may be beneficial. Teale and Embleton believe that they have obtained 
good results in certain cases. Shera expresses the belief that the local 
infection is too massive to permit of vaccine having any appreciable 
effect in the stage of consolidation. The frequent occurrence of pneu- 
mococcus septicemia as a part of the disease makes it unlikely that 
vaccination will be helpful. In delayed resolution vaccines are of value 
in some cases. Shera also states that empyema when it has reached the 
chronic stage may be benefited by specific vaccination. 

Other Diseases. Certain diseases of the accessory regions of the 
respiratory tract, including chronic median otitis and mastoiditis, have 
been treated by vaccination with the organism concerned. Results 
have been variable, but inasmuch as these represent somewhat isolated 
local infections it is reasonable to attempt vaccination in addition to 
the usual modes of treatment. 


When conjunctivitis becomes chronic, specific vaccination sometimes 
leads to improvement. The infecting agents include staphylococcus, 
streptococcus, bacillus pyocyaneous, Friedlander's bacillus and others. 
Autogenous vaccines may be employed in addition to other modes of 


treatment. Chronic conjunctivitis, due to the Morax-Axenfeld diplo- 
bacillus, is said to respond very well to vaccine treatment. In acute 
pneumococcus and gonococcus conjunctivitis, especially with ulcer, 
Allen advises early and vigorous vaccine therapy and reports good 
results. It is also stated that ophthalmia neonatorum sometimes im- 
proves rapidly under vaccine treatment. In none of these conditions, 
however, is it wise to neglect other forms of treatment. 


Typhoid Fever. Prophylactic vaccination has unquestioned value 
in the prevention of typhoid fever (page 285). Specific therapeutic 
vaccination has been the subject of experiment since the work of 
Fraenkel in 1893. The vaccines employed have been usually killed 
organisms either untreated or sensitized, administered either subcu- 
taneously or intravenously. Certain authors have also reported the use 
of living organisms, but this method has not been adopted. Gay, in his 
book, " Typhoid Fever," reports the following summary of results 
obtained by various methods : 


nK<, ., Total Estimates Bene- Mortal- 
Observers cases basedon fited ity 

Untreated vaccine subcutaneously .... 30 1001 512 46% 14-5% 

Sensitized vaccine subcutaneously .... 14 593 239 69% &.o% 

Untreated vaccine intravenously 22 501 233 62% 13.0% 

Sensitized vaccine intravenously 12 487 316 85% 11.0% 

It is usually stated that typhoid fever has a mortality of about 10 per 
cent., although in the American Civil War it exceeded 35 per cent, and 
in the Franco-Prussian, Spanish-American and Boer Wars it ranged 
between 8 and 14 per cent. The severity of epidemics varies consid- 
erably, but at the best there is little in the way of encouragement to be 
found in the table given above. The basis upon which improvement 
is estimated varies considerably with the different investigators and 
the figures are " distinctly affected by subjective influences." Gay has 
employed a sensitized vaccine administered intravenously and his re- 
sults in ninety -eight cases are summarized as follows : 





Aborted 33 

Benefited 32 

Unaffected ... 33 

The most significant figures in this table refer to those cases which 
were aborted. Careful study of various epidemics fails to show any 
instance where such a large percentage of the cases have aborted, and 
it therefore seems probable that the vaccination had some distinct value. 




No. of 




on _ 



































This rapid improvement appeared to be somewhat more striking in the 
moderate and mild cases than in those which were considered severe. 

Other investigators have noted that non-specific therapy has been 
quite as effective as the use of specific typhoid vaccine. Kraus found 
that colon bacilli were equally effective and others have confirmed this 
observation. Liidke has employed deutero-albumose, Weichardt al- 
bumin solutions, Nolf pepton and still others have employed such sub- 
stances as dextrose, colloidal gold and even normal salt solution. Gay 
admits that the non-specific form of therapy has been as effective as 
the use of sensitized typhoid vaccines, but urges the employment of 
typhoid vaccine because it may be kept indefinitely in dried form under 
conditions of strict asepsis and can readily be injected in exact amounts. 
He further states that " typhoid vaccine has the advantage over other 
protein preparations of building up the active immunity of the patient, 
and a sensitized vaccine will, in our experience, produce a higher grade 
of leucocytosis." 

Paratyphoid Fever. Rathery and others have used therapeutic 
vaccination in paratyphoid B fever. It was concluded that the treatment 
is useful, always improves general condition, often shortens the fever 
and has never led to harmful results. Others have found that typhoid 
vaccine is as effective in paratyphoid as in true typhoid fever and the 
non-specific therapy indicated above has also been effective. 

Dysentery. The vaccine treatment of dysentery is confined to the 
bacillary form and of these varieties the cases due to the Flexner 
bacillus and other related forms appear to do much better than those 
caused by the Shiga bacillus. Nolf, from his observations in the Belgian 
Army, concludes that vaccine therapy, when administered by the intra- 
venous route is the most effective therapeutic procedure in the more 
chronic forms of bacillary dysentery. His cases did not include those 
caused by the Shiga bacillus. Similar results had been reported by 
Baroni in the Roumanian Army. He employed either six injections of 
killed organisms or four injections of living vaccine. Kountze found 
that in typical cases of dysentery, vaccination produced immediate gen- 
eral improvement and reduction in the number of stools. The study of 
the therapy of this disease has been somewhat hampered by the failure of 
investigators to identify the strains of organisms concerned. Although 
the results with vaccination have been encouraging, it is by no means posi- 
tively proven that this mode of treatment is superior to serum treatment. 


The various forms of tuberculin are vaccines and treatment by their 
use is an example of vaccine therapy. The methods of preparation of 
the various tuberculins have been discussed (page 238). Koch's first 
work with tuberculins was stimulated by the hope that treatment with 
them might be effective. The use of the material in larger amounts 
than now seem necessary led to severe reactions on the part of the 
patients which in some instances were disastrous. For many years 
tuberculin therapy was considered extremely dangerous and was prac- 
ticed by very few clinicians. Recently, however, a more thorough 


knowledge of the proper precautions in treatment has been built up and 
satisfactory results are now reported. Applied to pulmonary tubercu- 
losis it has been followed by improvement in many cases, particularly 
in those under sanitarium treatment. It also is claimed to be an im- 
portant aid in the treatment of tuberculosis of the bones and joints 
and of the eye. Improvement has been reported also in cases of tuber- 
culous enteritis and mesenteric lymphadenitis. Kleinberg, however, 
maintains that only a small proportion of bone and joint cases improve, 
that the majority show no improvement and that in some cases relapses 
occurred and new abscesses appeared. 

Apparently the most suitable patients for tuberculin therapy are 
those with incipient tuberculosis or old cases of fibroid phthisis with 
fair or good nutrition. Advanced or moderately advanced cases may 
be so treated if the general condition is good. Hamman and Wolman 
do not consider marked general weakness, fever, cardiac disease, 
nephritis, epilepsy, syphilis of themselves contraindications but rather 
unfortunate complications which may prevent specific treatment. 

The injections are given subcutaneously at the lower angle of the 
scapula. In order to observe whether or not reaction occurs the in- 
jections are given in the afternoon after the patient's temperature has 
been taken. This avoids mistaking an accidental afternoon rise of tem- 
perature for a rise due to the tuberculin. Hamman and Wolman recom- 
mend the following range of doses : 

Tuberculin Initial dose Maximal dose 

Old tuberculin 0.000,000,1 to 0.000,001 c.c. I. c.c. 

New tuberculin 0.000,001 to 0.000,1 c.c. 2. c.c. 

Bacillus emulsion 0.000,001 to 0.000,1 c.c. 2. c.c. 

Three classes of patients are recognized: (i) children, (2) patients 
who exhibit a slight fever or are not in good condition, (3) patients in 
good general condition. The smaller initial doses are for patients of 
the first two groups, the larger for patients in the third group. Other 
forms of tuberculin are employed, but the types noted above have been 
given the most extensive trial. Provided reactions are absent or very 
slight, the injections may be repeated every three or four days. Tuber- 
culin has been given by mouth, but is absorbed irregularly and may pro- 
duce unexpected reactions. It has also been administered intrafocally 
in tuberculous pleurisy, tuberculous peritonitis, lupus and tuberculosis 
of the joints and of the tunica vaginalis. Results have in some instances 
been encouraging. The local reactions include pain, tenderness and 
swelling. General reactions are exhibited by rise in temperature, 
malaise, headache, insomnia, rapid pulse, loss of weight. 

Shiga has recently reported upon the use of a " serovaccine." This 
is designed especially for prophylactic injection in those who by virtue 
of family relations, constitution or other conditions are predisposed to 
the disease and for early incipient cases. He claims to have obtained ex- 
cellent results by weekly vaccination with increasing amounts of the sero- 
vaccine followed after fifteen injections by two graded doses of living 
avirulent tubercle bacilli. The method is prophylactic rather than curative. 


Abderhalden, building-stone theory 

of, 30 
Abrin, 70 

Acquired immunity, 21 
actively, 22 
artificially, 22 
naturally, 21 
Agglutinability of bacteria, alterations 

of, 92 

Agglutination, group reactions, 85 
influence of electrolytes on, 90 
of heat on, 89 
of hydrogen, ion concentration 

on, 91 

inhibition zones in, 89 
mechanism of, 91 
physical basis of, 93 
Agglutinins, absorption of, 86 
bacterial, 79 
immune, 80 

production of, 80 
macroscopic titration of, 83 
main, 80 
major, 80 

microscopic titration of, 84 
minor, 80 
nature of, 92 
normal, 80 
partial, 80 

preliminary titration of, 82 
production of anti-typhoid, 81 
specificity of, 85 
Aggressins, 4 

Amboceptor, activation of by comple- 
ment, 181 
and complement in normal hemo- 

lysins, proportions of, 135 
partial, 123 
Anaphylactic poisons, 218 

shock, blood pressure in, 214 

coagulability of blood in, 215 
distention of lungs in, 213 
ferments in, 215 
in guinea-pigs, 212 
in man, 230 
metabolism in, 214 
methods of preventing, 216 
Anaphylactoid phenomena, 224 
Anaphylatoxin, 219 
Anaphylaxis, 209 

cellular theories of, 220 
cross reactions in, 217 
group reactions in, 217 
intoxicating injection in, 211 
passive, 216 

period of. incubation in, 211 
physical theories of, 222 
reaction, 212 
sensitization in. 210 

Anaphylaxis, specificity of, 217 

theories of, 218 

Anthrax, serum therapy of, 259 
Anti-aggressins, 5 
Anti-amboceptors, 136 
Anti-anaphylaxis, 215 
Antibodies, Bordet antibody, 170 
leucocyte antibody, 168 
production at site of injection, 35 
Antibody, definition of, 22 
formation, site of, 33 
Anti-complementary action of cells, 

tissue extracts and body-fluids, 183 
Anti-complements, 137 
Anticorps leucocytaire, 168 
Anti-dysentery sera, therapeutic use 

of, 63. 
Antiferment, 248 

determination in blood serum, 249 
Antiferment-ferment balance, 247 
Antigen, definition of, 22 
Anti-rabic vaccination, effects of, 284 
in man, 284 
results of, 285 
Antitoxins, formation of, 41 

influence of temperature on, 43 
nature of, 43 
Anti-typhoid vaccination, complications 

of, 290 

contraindications to, 291 
duration of protection in, 290 
method of, 287 
prophylactic value of, 288 
Asthma, cutaneous tests in, 234 

vaccine treatment of, 299 
Auto-serum therapy, 264 
in syphilis, 265 

Bacteremia, 13 

Bacterial precipitins, production of, 108 

products, immunization with, 24 

toxins, classification of, 40 

vaccine, definition of, 273 
killed, 275 
preparation of, 275 
Bacteriolysins, 144 
Bacteriolysis, bioscopic method for, 149 

Buxton's method for, 148 

in vitro, 146 

Wright's method for, 147 
Bacteriotropins, 162 
Bleeding a rabbit, 83 

a guinea-pig, 127 
Blood antigen, 117 

groups classification, Jansky, 99 
Moss, lop 

serum, therapeutic employment of, 

transfusion, reactions to, 105 




Bordet-Gengou phenomenon, 173 

laboratory demonstration of, 

Botulinus antitoxin, 65 

toxin, 65 
Botulism, use of immune sera in, 65 

Canine distemper, cutaneous reaction 

in, 244 

Carbuncles, vaccine treatment in, 298 
Cataphylaxis, 8 
Chemical agencies, anti-complementary, 


Chemotaxis, 152 
Cholera, vaccination against, 291 

serum therapy of, 258 
Cobra lecithid, 141 
Colloid shock, 225 
Complement, alterations of amount of, 


deviation, 148 
distribution of, 126 
end-piece of, 133 
fixation, acid- fast, 205 
delicacy of, 177 
group reactions in, 177 
inhibition zones in, 176 
tests, 206 

in echinococcus cyst, 207 

in glanders, 206 

in gonococcus infections, 


in malignant tumors, 207 
in smallpox, 206 
in sporotrichosis, 207 
in syphilis, 186 
in tuberculosis, 203 
in typhoid fever, 206 
in whooping-cough, 207 
fixing bodies, amboceptor, nature 

of, 180 

relation of to other im- 
mune bodies, 178 
fractions, 133 
in hemolysis, influence of amount 

of, 121 

inhibition of other than by fixa- 
tion, 182 

method of obtaining, 127 
mid-piece of, 133 
multiplicity of, 131 
nature of, 129 
origin of, 128 
preservation of, 130 
proportions of in normal hemoly- 

sins, 135 
titration of, 119 
variability of, 131 
Complementary activity, influence of 

lipoids on, 183 
Complementoids, 132 
Conglutinin, 106, 126 
Crotin, 71 
Curcin, 71 

Cutaneous reactions, in canine dis- 
temper, 244 

Cutaneous reactions, in glanders, 244 
in gonococcus infections, 242 
in hypersusceptibility, delicacy 

of, 235 

technic of, 234 
theories of, 236 

in hyphomycetes infections, 244 
in leprosy, 244 
in meningococcus infections, 


in pneumococcus infections, 243 
in pregnancy, 244 
in sporotrichosis, 244 
in typhoid fever, 242 
to vaccine virus, 243 
Cystitis, vaccine treatment of, 297 
Cytolysins, 115 

organ specificity of, 143 
Cytolysis, summary of, 149 
Cytotoxins, autocytotoxins, 144 
heterocytotoxins, 144 
isocytotoxins, 144 
lens, 144 
specificity of, 142 

Danysz effect (or phenomenon), 50 
Dead bacteria, immunization with, 23 
Defensive ferments, 245 
Desensitization in hypersusceptibility, 

Diphtheria, active immunization against, 


antitoxin, dosage of units of, 53 
injection scheme for produc- 
tion of, 42 

standardization of, 44 
technic of producing, 42 
therapeutic use of, 51 
titration of, 46 
carriers, anti-bacterial serum in 

treatment of, 262 
natural immunity to, 53 
Schick test in, 53 
toxin, technic of producing, 42 
Drug idiosyncrasies, 237 
Duck-bill platypus, 76 
Dysentery antitoxin (serum therapy), 


toxin, 62 

vaccination against, 294 
vaccine treatment of, 302 

Eczema, vaccine treatment of, 299 

Eel serum, 75 

Ehrlich classification of immune bodies, 


hypothesis, criticism of, 28 
side-chain theory, 26 
objections to, 49 
Endotoxins, 7 
Erythrocytes, chemical agglutination of, 


fragility of, 138 
iso-hemagglutinins, 98 
iso-hemolysins, 136 
Esterases, technic of determining, 247 



Exotoxins, 7, 40 

Eye, diseases of, vaccines in, 300 

Ferment-anti ferment balance, 247 
Ferments, defensive, 245 

immune, 246 

in blood, 246 

specificity of, 245 

Food adulteration, detection of, 113 
Furunculosis, vaccine treatment of, 298 

Gas gangrene, prophylactic use of sera 

in, 68 

serum treatment of, 67 
use of immune sera in, 67 
Glanders, cutaneous reaction in, 244 
Gonococcus infections, cutaneous reac- 
tions to, 242 
serum therapy of, 263 
vaccine treatment of, 297 

Hay fever, toxins in, 233 
Hemagglutinins, 98 

auto-hemagglutinins, 98 
hetero-hemagglutinins, 98 
immune hetero-hemagglutinins, 98 
iso-hemagglutinins, 98 
normal hetero-hemagglutinins, 98 
Hemolysins, 116 

auto-hemolysins, 116 
bacterial, 139 
collection of immune, 118 
immune hetero-hemolysins, 117 
iso-hemolysins, 136 
preparation of immune, 117, 118 
titration of immune, 118 
vegetable, 140 
venom, 141 

Hemolysis, chemical, 139 
group reactions in, 123 
physical, 138 
Hemolytic amboceptor-antigen union, 

dissociation of, 122 
and antigen, quantitative rela- 
tions of, 120 
and complement, quantitative 

relations of, 119 
relative affinities of, 120 
selective absorption of, 121 
mechanism of operation of, 125 
nature of, 124 
rate of absorption by blood 

cells, 122 
specificity of, 123 
antigen, nature of, 124 

quantitative relations of, 120 
complement, quantitative relations 

of, 119 

relative affinities of, 120 
selective absorption of, 121 
Hemophagocytosis, 162 
Hemotoxins, bacterial, 69 
Hetero-hemolysins, normal, 134 
Hog-cholera, serum therapy of, 270 
Host and parasite, mutual relations of, I 
factors favoring, 14 

Hyperleucocytosis, specific, 170 
Hypersusceptibility, 208 

delicacy of cutaneous tests in, 235 

natural, 230 

occurrence of, 208 

technic of cutaneous tests in, 234 

tests for, 233 

theories of cutaneous reactions in, 


Hyphomycetes infections, cutaneous re- 
action in, 244 

Immune human serum, treatment with, 

reactions, specificity of, 29 

sera, anti-hemolytic activity of, 185 
Immunity, as result of vaccination, 281 

function of precipitation in, 114 

relation of anaphylaxis to, 226 

theories of nature of, 26 

types of, 16 
Immunization, active, 15 

passive, 25 
Infections, primary, 13 

mixed or multiple, 13 

secondary, 13 

terminal, 13 

Infection, production of, n 
Infectious disease, course of, 15 

non-specific therapy of, 30 
Inflammation, cellular participation, 170 

in resistance, influence of, 172 
Influenza, vaccination against, 295 
Invader, entrance of, n 

factors favoring, 13 

inhibiting, 14 
Iso-hemagglutinins, 99 

characters of, 100 

incidence of, 100 

in lower animals, 101 

mechanism of, 101 

methods for testing human blood 
for, 103 

Rous and Turner method, 103 
with standard sera, 103 

relation of to blood transfusion, 

Iso-hemolysins, normal, 136 

Leprosy, cutaneous reaction in, 244 
Leucocyte enzymes, 168 

extracts, for therapeutic purposes, 


Leucocytes, bactericidal extracts of, 167 
Leucoprotease, 168 
Leucotoxins, 143 
Lipovaccines, 277 
Luetin reaction, 242 
Lymphocyte ferments, 170 

resistance to cancer, 171 

Macrocytase, 173 
Mass action, law of, 50 
Meningococcus infection, 254 

cutaneous reaction to, 243 

serum therapy of, 254 
Microcytase, 173 

3 o8 


Natural hemolysins, fixation of comple- 
ment of, 182 
immunity, 16 

classification of, 18 

family, 20 

individual, 20 

inherited, 20 

racial, 18 

species, 18 

Neisser-Wechsberg phenomenon, 147 
Normal serum, therapeutic use of, 270 

Opsonins, 158 

as " facultative " amboceptor, 161 
experimental demonstration of, 159 
for cells other than bacteria, 162 
immune, 161 
normal, 159 

specificity and other characters of, 

Ozena, vaccine treatment of, 299 

Parasite and host, mutual relations of, I 
Parasitic protozoa, poisons of, 75 
Parasitism, half parasites, 2 
pure parasites, 2 

saprophytes, 2 
Paratyphoid fever, vaccination against, 

. 2g 5 
vaccine treatment of, 302 

Pertussis, vaccination against, 294 
vaccine treatment of, 300 
Pfeiffer phenomenon, 144 

demonstration of, 145 
Phagocytic cells, influences operating 

upon, 165 
types of, 153 
Phagocytosis, 151 

analysis of mechanism of, 165 

digestion of bacteria in, 153 

experimental demonstration of, 155 

functions of, 154 

influence of phagocyte and ingested 

elements on, 163 
of temperature on, 157 

ingestion of foreign body in, 153 

mechanism of, 155 

physical basis of, 156 

process of, 152 

relation of bacterial virulence to, 164 

surface tension in, 156 
Phagolysis, 155 
Phasin, 71 
Phytotoxins, 69 
Plague, 260 

serum therapy of, 260 

vaccination against, 293 
Plant pollens, 231 
Pneumococcus infections, 256 

cutaneous reaction to, 243 
Pneumonia, serum treatment of, 256 

vaccination against, 292 

vaccine treatment of, 300 
Pneumotoxin, 243 
Poisonous fish, 75 

substances, production of, 6 

Poisons, bees, wasps and hornets, 74 

centipedes, 74 

duck-bill platypus, 76 

of parasitic protozoa, 75 

scorpion, 74 

spider, 74 

toads, frogs and salamanders, 75 

vegetable, 69 
Poliomyelitis, acute anterior, serum 

therapy of, 268 
Pollantin, 233 
Precipitation, 106 

biological relationships based on, in 

delicacy of, 109 

experimental demonstration of, 108 

functions of in immunity, 114 

nature of reaction of, 107 

organ specificity of, 1 12 

physical basis of, 109 

practical application of, no 
Precipitin test in game laws, 1 14 
Pregnancy, Abderhalden test, 249 

cutaneous reaction in, 244 
Prophylactic vaccination, 272 
Proteases, technic of determining, 247 
Proteins, poisonous bacterial, 7 
Ptomains, 6 

Pyelitis, vaccine treatment of, 298 
Pyemia, 13 

Rabic vaccine, preparation of, 283 
Rabies, active immunization in, 283 

vaccination against, 282 
Resistance, factors operating against, 14 
Rhinitis, vaccine treatment of, 299 
Ricin, 70 

Rinderpest, serum treatment of, 269 
Ringworm, vaccine treatment of, 299 
Robin, 71 

Sapremia, 13 

Septicemia, 13 

Serum, anti-anthrax, 259 

anti-bacterial, in treatment of diph- 
theria carriers, 262 

anti-cholera, 258 

anti-gonococcus, 263 

anti-hog-cholera, 270 

anti-meningococcus, 254 

anti-plague, 260 

anti-pneumococcus, 256 

anti-poliomyelitis, 268 

anti-streptococcus, 253 

disease, accelerated reaction, 229 

delayed reaction, 228 
Smallpox vaccination, 278 

methods of, 280 

vaccine, preparation of, 279 
Sporotrichosis, cutaneous reaction in, 244 
Streptococcus infections, serum therapy 

of, 253 

Suppurative nephritis, vaccine treat- 
ment of, 298 

Syphilis, auto-serum therapy in, 265 
Syphilitic amboceptor, 190 
nature of, 191 

antigen, nature of, 189 



Tests, Abderhalden, 249 Vaccine treatment, in eczema, 299 

Dreyer, 96 in furunculosis, 298 

forensic blood, no .in gonorrhea, 297 

tuberculin, 238 in ozena, 299 

Widal, 85 in paratyphoid fever, 302 

Tetanolysin, 57 in pertussis, 300 

Tetanospasmin, 58 in pneumonia, 300 

Tetanus, serum treatment of, 60 in pyelitis, 298 

antitoxin, 56 in rhinitis, 299 

prophylactic use of, 59 in ringworm, 299 

therapeutic use of, 58 in suppurative nephritis, 298 

toxin, 56 in tuberculosis, 302 

route of absorption of, 58 in typhoid fever, 301 

Thigmotropism, 171 virus, cutaneous reaction to, 243 

Toxin-antitoxin union, 47 Vaccines, definition of, 273 

Ehrlich theory of, 47. dosage of, 277 

Toxins, bacterial, 38 method of counting, 276 

gas bacillus, 67 types of, 274 

general nature of, 38 autogenous, 275 

injury of, 39 killed bacterial, 275 

L+ dose of, 46 living, 274 

LQ dose of, 46 mixed, 275 

minimum lethal dose of, 45 sensitized, 274 

pathological effects of, 41 stock, 275 

pollen, 71 tetra, 287 

true, 7 triple, 287 

Tuberculin reaction, 238 Vaccinia, 281 

conjunctival, 239 Vaccinoid, 243 

cutaneous reaction of, 239 Venom cobra, clinical tests, 142 

general, 238 Venoms, pathological effects of, 73 

intracutaneous, 239 production of antisera for, 73 

percutaneous, 239 snake, 71 

specificity of, 241 Virulence, 2 

theories of, 240 alteration of, 8 

utility of, 241 basis of, 3 

Tuberculosis, complement fixation in decrease of, 9 

203 demonstration of, 3 

serum treatment of, 263 increase of, 8 

vaccine treatment of, 302 Virulins, 5 
Typhoid fever, cutaneous reaction in, 

242 Wassermann reaction, 186 

serum treatment of, 263 antigen for, 187 

vaccination against, 285 complement for, 191 

vaccine treatment of, 301 dependability of, 202 

vaccine, preparation of, 286 diagnostic value of, 201 

Typhus fever, vaccination against, 294 end-piece in, 134 

hemolytic system for, 194 

Vaccination, against cholera, 291 influence of temperature upon, 

dysentery, 294 196 

influenza, 295 interpretation of results of, 202 

pertussis, 294 modifications of, 200 

plague, 293 post-mortem, 203 

pneumonia, 292 preservation of erythrocytes 

rabies, 282 for, 195 

typhoid and paratyphoid fevers, quantitative results with, 203 

285 reading, 199 

typhus fever, 294 specificity of, 200 

immunity as result of, 281 on spinal fluid, 203 

unfavorable results of, 282 technic of, 196 

Vaccine therapy, 296 test, protocol of, 199 

treatment, in asthma, 299 table of methods of perform- 
in carbuncles, 298 ing, 192 
in cystitis, 297 Weber-Fechner law, 152 
in diseases of the eye, 300 
in dysentery, 302 Zootoxins, 71 

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